Chapter 3 Biology quiz

What is changing velocity?

1. IF EITHER THE SPEED OR THE DIRECTION CHANGES (OR IF BOTH CHANGE), THEN THE VELOCITY CHANGES a) a car on a curved track, for example, may have a constant speed, but, because its direction is changing, its velocity is not constant b) it is accelerating

What is the difference between mass and volume?

1. It is also easy to confuse mass and volume 2. when we think of a massive object, we often think of a big object a) an object's size (VOLUME), however is not necessarily a good indication of its mass b) which is easier to get moving: a car battery or an empty cardboard box of the same size? c) so, we find that mass is neither weight nor volume 3. VOLUME: THE QUANTITY OF SPACE AN OBJCT OCCUPIES. ANOTHER WORD FOR "LOUDNESS" OF SOUND

What are the kinematic equations

1. v=v₀ + at 2. ∆x=v₀t + 1/2at² 3. v² = v₀² + 2a∆x

What are the kinematic equations under gravity?

1. v=v₀ -gt 2. ∆y = v₀t - 1/2gt² 3. v² = v₀² - 2g∆y

What are velocity vectors? How can you solve a vector problem using a parallelogram?

1. whereas speed is a measure of "how fast," velocity is a measure of both "how fast" and "in which direction." a) if speedometer in a car reads 100 kilometers per hour (km/h), you know your speed b) if there is also a compass on the dashboard, indicating that the car is moving due north, for example, you know your velocity -100 km/h north c) to know your velocity is to know your speed and your direction 2. SPEED IS A SCALAR QUANTITY AND VELOCITY IS A VECTOR QUANTITY 3. refer to airplane example in figure 3.12 of book

What is instantaneous speed?

INSTANTANEOUS SPEED: the speed at any instant 1. things in motion often have variations in speed a) a car, for example, may travel along a street at 50km/h, slow to 0 km/h at a right light, and speed up to only 30 km/h because of traffic 2. you can tell the speed of the car at any instant by looking at its speedometer 3. a car traveling at 50km/h usually goes at that speed for less than 1 hour a) if it did go at that speed for a full hour, it would cover 50 km b) if it continued at that speed for half an hour, it would cover half that distance: 25 km c) if it continued for only 1 minute, it would cover less than 1km

What is speed? How is it calculated?

SPEED: HOW FAST SOMETHING MOVES; THE DISTANCE AN OBJECT TRAVELS PER UNIT OF TIME; THE MAGNITUDE OF VELOCITY a) Speed = distance/time b) delta notation: v = ∆x/∆t c) distance formula: ∆x= v x ∆t c) units: m/s 1. average speed = total distance covered/time interval 2. before the time of Galileo, people described moving things as simply "slow" or "fast" a) such descriptions were vague 3. Galileo is credited with being the first to measure speed by considering the distance covered and the time it takes a) he defined speed as the DISTANCE COVERED PER UNIT OF TIME b) interestingly, Galileo could easily measure distance, but in his day measuring short times was no easy matter c) he sometimes used his own pulse and sometimes the dripping of drops from a "water clock" he devised 4. two types of speeds: a) average speed b) instantaneous speed 5. Speed is a scalar quantity

a school bus slows to a stop with an average acceleration of -2.0 m/s². Show that it takes 5.0s for the bus to slow from 10.0m/s to a position of rest

V= Vo + at. t=vf-vo/a t=0-10.0m/s/-2.0m/s² = 5s

While you are in a bus that moves at 100 km/h you walk from the back to the front at 10 km/h. What is your speed relative to the road outside? a) 110km/h b) 100 km/h c) 90 km/h d) 10 km/h

a) 110 km/hr

what is the average speed of a horse that gallops 100 m in 8 s? How about if it gallops 50 m in 4s?

a) average speed = total distance covered/travel time = 100m/8s = 12.5m/s b) average speed= total distance covered/travel time = 50m/4s =12.5m/s

What is the net force when a pair of 5N forces simultaneously act in the same direction on an object? a) 5N b) 10N c) 0 N d) 7.5 N

b) 10N

How much support force acts on a 200 N girl standing on a weighing scale? a) no support force unless she stands on the floor b) 200 N c) less than 200 N d) more than 200 N

b) 200 N

Which of Newton's laws does the equilibrium rule illustrate? a) Newton's law of gravity b) Newton's first law c) Newton's second law d) Newton's third law

b) Newton's first law

Newton said that something was needed to change the motion of an object. A clear reading of his first law tells us that what is needed is___________ a) a net force b) a non-zero net force c) a force d) no force at all

b) a non-zero net force

Galileo discovered that when air resistance can be neglected, all objects fall with the same ________ a) energy of motion b) acceleration c) distance d) speed

b) acceleration

When we are talking about how quickly "how fast" changes, we're talking about__________ a) increases in falling distance b) acceleration c) free fall physics d) the difference between speed and velocity

b) acceleration

the unit of mass is the kilogram, and the unit of weight is the________ a) m/s² b) newton c) metric mass d) kilogram also

b) newton

A ball rolling down an inclined plane each second picks up________ a) decreasing amounts of speed each second b) the same amount of speed each second c) increasing amounts of speed each second d) acceleration, not speed

b) the same amount of speed each second

A ball freely falling at 20 m/s will in the next second have a speed of___________ a) 10 m/s b) 20 m/s c) 30 m/s d) more than 30 m/s

c) 30 m/s

In its first second of free fall, a dropped softball will fall a vertical distance of ______. a) 20 m b) 15 m c) 5 m d) 10 m

c) 5 m

If while riding in a smooth riding train, you toss a coin upward, the coin will normally land_____ a) off to the side of your location when you toss the coin b) in front of you c) in your hand d) behind you

c) in your hand

as a skydiver gains speed in falling through the air, air resistance____________ a) decreases b) becomes negligible when terminal speed is reached c) increases d) cancels weight

c) increases

a speedometer normally measures_________ a) velocity b) distance traveled c) instantaneous speed d) average speed

c) instantaneous speed

Which BEST describes what occurs when a body accelerates? a) change in direction b) change c) change in velocity d) change in velocity per unit time

d) change in velocity per unit time

the difference between speed and velocity involves a) the magnitude of. each b) path length c) acceleration d) direction

d) direction

air resistance on a parachutist at terminal speed____________ a) is the same for both a heavy and light person with the same size parachutes b) is less for a heavy person c) no longer depends on speed d) is greater for a heavier person

d) is greater for a heavier person

a 1kg stone and a 10 kg stone have the same acceleration in free fall because___________ a) air resistance has no effect b) they both fall equally c) the force of gravity is the same on each d) the ratio of weight to mass is the same for each

d) the ratio of weight to mass is the same for each

A crate sits at rest on a factory floor. Friction between the crate and floor occurs________ a) even when no pushing occurs b) only if the crate is pushed vertically as well as horizontally c) only if the crate is sliding d) when the crate is pushed horizontally, whether sliding or not

d) when the crate is pushed horizontally, whether sliding or not

If a car travels with an average speed of 60 km/hr for an hour, it will cover a distance of 60 km. (a) how far would the car travel if it moved at this rate for 4h? (b) for 10 hours?

distance travelled = average speed x time of travel a) distance = 60 km/hr x 4h = 240 km b) distance = 60km/hr x 10h = 600km

A ball is thrown straight up with an initial speed of 30m/s a) how much time does it take for the ball to reach the top of the trajectory? b) show that the ball will reach a heigh of 45 m (neglecting air resistance)

hang time: h=(1/2)v₀²/g or 2xt = 2v₀/g a) 3s b) (1/2)(30 m/s)²/10 m/s² = (1/2)(30 x 30/10) = 90/2 m = 45 m

A school bush slows to a stop with an average acceleration of -2.0 m/s². Show that it takes 5.0s for the bus to slow from 10.0 m/s to a position of rest

t= v-v₀/a = 0-10m/s/-2m/s² = 5s

A car moving with constant acceleration ax= 0/5 m/s² along the x-axis crosses the origin with velocity v₀x = -10 m/s. Find the position of the car when its velocity is vx= -5 m/s

v²x = v²₀x + 2ax∆x → ∆x = v²x = v²₀x/2ax = ((-5 m/s)² - (-10m/s)²)/ 2(0.5 m/s²) = -75 m

What are the formulas for speed velocity, and acceleration?

∆x= distance covered ∆→x = displacement ∆→v = change in velocity ∆t= time 1. speed, v = ∆x/∆t 2. velocity, →v, ∆→x/∆t 3. acceleration, →a = ∆→v/∆t

A particle moving along the x axis slows down with constant acceleration from velocity 20 m/s to 10 m/s in ∆t = 10s. What is the x component of its acceleration measured in m/s²

𝒂𝒙 = v₂x- v₁x/∆t = 10m/s - 20m/s/10s = -1 m/s²

How was Aristotle's ideas on motion received?

1. Aristotle taught that all motions are due to the nature of the moving object or due to a sustained push or pull a) provided that an object is in its proper place, it will not move unless subjected to a force b) except for celestial objects, the normal state is one of rest 2. Aristotle's statements about motion were a beginning in scientific thought, and, although he did not consider them to be the final words on the subject, his followers for nearly 2000 years regarded his views as beyond question 3. Renaissance times was the notion that the normal state of objects is one of rest a) since it was evident to most thinkers until the 16th century that Earth must be in its proper place, and since a force capable of moving Earth was inconceivable, it seemed quite clear to them that Earth does not move

What is constant velocity?

1. Constant speed means steady speed a) something with constant speed doesn't speed up or slow down 2. Constant velocity, on the other hand, MEANS BOTH CONSTANT SPEED AND CONSTANT DIRECTION 3. Constant direction is a straight line-the object's path doesn't curve a) so constant velocity means MOTION IN A STRAIGHT LINE AT A CONSTANT SPEED

What is the equilibrium rule? What is mechanical equilibrium?

1. EQUILIBRIUM RULE The vector sum of forces acting on a non-accelerating object is equal to zero. In equation for equilibrium: ∑→F=0 or ∑F=0 a) on an object or system of objects in mechanical equilibrium, the sum of forces equals zero b) also ∑λ = 0; the sum of the torques equals zero c) the symbol ∑ stands for "the vector sum of" and F stands for "forces" d) for a suspended object at rest, the rule says that the forces acting upward on the object must be balanced by other forces acting downward to make the vector sum equal to zero (vector quantities take direction into account, so if upward forces are +, downward ones are -, and when added, they actually subtract 2. a string holding up a bag of flour has two forces acting on the bag of flour: a) tension force in string acts upward b) force due to gravity acts downward c) both are equal in magnitude and opposite in direction d) when added, they cancel to zero e) so, the bag of flour remains at rest 3. the vector sum of forces acting on a non accelerating object equals zero a) in equation for: ∑Ni=1 →Fi=0 2. MECHICAL EQUILIBRIUM: the state of an object or system of objects for which any impressed forces cancel to zero and no acceleration occurs and no net torque exists; that is, ∑λ = 0 and ∑F=0 a) the fact that no net force acts on the bag of flour, means that the flour is in mechanical equilibrium

What is equilibrium? What is the equilibrium test?

1. EQUILIBRIUM: A STATE OF NO CHANGE WITH NO NET FORCE ACTING a) an object at rest and an object moving at a constant speed in a straight line path is also in equilibrium 2. There are two types of equilibrium: a) static equilibrium b) dynamic equilibrium 3. Example of static equilibrium: hockey puck at rest on slippery ice 4. Example of dynamic equilibrium: hockey pick sliding at constant speed on slippery ice 5. EQUILIBRIUM TEST: whether something undergoes CHANGE in motion a) example: a crate at rest is in static equilibrium (no change in motion) b) example: when pushed at a steady speed, it is in dynamic equilibrium (no change in motion ) c) it follows from newton's first law that an object that is under the influence of only one force cannot be in equilibrium d) the net force couldn't be zero e) only when two or more forces act on an object can it be in equilibrium f) we can test whether or not something is in equilibrium by noting whether or not it undergoes changes in its state of motion 6. a zero net force on an object doesn't mean that the object must be at rest, but that its state of motion remains unchanged a) it can be at rest or moving uniformly in a straight line 7. the equilibrium rule, ∑F=0, provides a reasoned way to view all things at rest- balancing rocks, objects in your room, or the steel beams in bridges or in building construction a) whatever their configuration, if an object is in static equilibrium, all acting forces always balance to zero o b) the same is true of objects that move steadily, not speeding up, slowing down, or changing direction c) for dynamic equilibrium, all acting forces also balance to zero d) the equilibrium rule is one that allows you to see more than meets the eye of the casual observer e) it's nice to know the reasons for the stability of things in our everyday world

How does a free fall object react to being thrown straight up in the air?

1. once released, an object thrown straight upward continues to move upward for a time and then comes back down a) at the object's highest point, when it is changing its direction of motion from upward to downward, its instantaneous speed is zero b) then it starts downward JUST AS IF IT HAD BEEN DROPPED FROM REST AT THAT HEIGHT 2. during the upward part of this motion, the object slows as it rises a) it should come as no surprise that it slows at the rate of 10 meters per second each second-the same acceleration it experiences on the way down b) the instantaneous speed at points of equal elevation in the path is the same whether the object is moving upward or downward c) the velocities are opposite, of course, because they are in opposite directions d) note that the downward velocities have a negative sign, indicating the downward direction (it is customary to call up positive and down negative) e) whether the object is moving upward or downward, its acceleration is 10 m/s² the whole time

Explain how normal force acts on an elevators?

1. Elevators action depends on the acceleration of the elevator a) if the elevator is moving at a constant speed: you feel your normal weight b) if the elevator is moving with increasing speed up: you feel greater than the normal weight c) if the elevator is moving at an decreasing speed, downwards: you feel less than the normal weight d) the elevator breaks and you are in free fall: zero weight 2. Example: Normal Force on a level surface: ∑Fy= may n-mh = 0 n=mg a) ay can get 0 in 2 ways: (1) at rest (2) when the elevator is moving up or down with constant velocity b) some y forces (Fy) are equal to may = m(0) because you don't have a force on the y axis so Fn=mgcosθ 3. Example: The normal force on a level surface under acceleration when the acceleration is going up: ∑F = ma→ n-mg = ma n=ma + mg n= m(g+a) a) if a = 0, then n=mg 4. The normal force on a level surface under acceleration when the acceleration is going down: mg - n =ma → n= mg-ma = m(g-a) a) if a = 0, then n=mg 5. when an object is at rest, the normal force is the weight 6. when force is applied, the normal force is not zero because force has been supplied a) the normal force is changed by the amount of force applied on the object and the angle is it applied 7. the acceleration is also affected by these 8. maximum reaction equal to its weight is reached with a horizontal flat surface and lessens with inclination 9. friction opposes motion so it decreases acceleration

What is an example of weightlessness

1. Example of weightlessness: a) no support force b) an astronaut is weightless because he or she is not supported by anything. The body responds as if gravity forces were absent, and this gives the sensation of weightlessness 2. Away from Earth's surface, where the influence of gravity is less, a 1 kilogram brick weighs less a) if would also weigh less on the surface of planets that have weaker gravity than Earth b) on the Moon's surface, for example, where the gravitational force on things is only one sixth as strong as on Earth, a 1 kilogram brick weighs about 1.6 newtons (or 0.36 pound) 3. on planets with stronger gravity, it would weigh more, but the mass of the brick is the same everywhere a) the brick offers the same resistance to speeding up or slowing down regardless of whether it's on Earth, on the Moon, or on any other body attracting it b) in a drifting spaceship, where a scale with a brick on it reads zero, the brick still has mass c) even though it doesn't press down on the scale, the brick has the same resistance to a change in motion as it has on Earth d) just as much force would have to be exerted by an astronaut in the spaceship to shake it back and forth as would be required to shake it back and forth while on Earth e) you'd have to provide the same amount of push to accelerate a huge truck to a given speed on a level surface on the Moon as on Earth f) the difficulty of lifting it against gravity (weight), however, is something else g) mass and weight are different from each other

What is Galileo's concept of inertia? How did he destroy Aristotle's assertions?

1. Galileo demolished Aristotle's assertions in the 1500s 2. Galileo's discovery: a) objects of different weight fall to the ground at the same time in the absence of air resistance b) a moving object needs no force to keep it moving in the absence of friction 3. Force: a push or a pull 4. INERTIA: a property of matter to resist changes in motion a) depends on the amount of matter in an object (its mass) b) INERTIA: SLUGGISHNESS OR APPARENT RESISTANCE OF AN OBJECT TO CHANGE ITS STATE OF MOTION. MASS IS THE MEASURE OF INERTIA c) inertia isn't a kind of force; its a property of all matter to resist changes in motion 5. Galileo tested his hypothesis by experimenting with the motions of various objects on plane surfaces titled at various angles a) he noted that balls rolling on downward sloping planes picked up speed, while balls rolling on upward-sloping planes lost speed b) from this he reasoned that balls rolling along a horizontal plane would neither speed up nor slow down c) the ball would finally come to rest not because of its "nature," but because of friction d) this ideas was supported by Galileo's observation of motion along smoother surfaces: when there was less friction, the motion of objects persisted for a longer time; the less the friction, the more the motion approached constant speed e) he reasoned that, in the absence of friction or other opposing forces, a horizontally moving object would continue moving indefinitely 6. This assertion was supported by a different experiment and another line of reasoning a) Galileo placed two of his inclined planes facing each other b) he observed that a ball released from a position of rest at the top of a downward sloping plane rolled down and then up the slope of the upward sloping plane until it almost reached its initial height c) he reasoned that only friction prevented it from rising to exactly the same height, for the smoother the lanes, the closer the ball rose to the same height d) then he reduced the angle of the upward sloping plane e) again the ball rose to the same height, but it had to go farther f) additional reductions of the angle yielded similar results; to reach the same height, the ball had to go farther each time g) he then asked the question, "if I have a long horizontal plane, how far must the ball go to reach the same height?" h) the obvious answer is "forever-it will never reach its initial height" 7. Galileo analyzed this in still another way a) because the downward motion of the ball from the first plane is the same for all cases, the speed of the ball when it begins moving up the second plane is the same for all cases b) if it moves up a steep slope, it loses its speed rapidly c) on a lesser slope, it loses its speed more slowly and rolls for a longer time d) the less the upward slope, the more slowly the ball loses its speed e) in the extreme case in which there is no slope at all-that is, when the plane is horizontal-the ball should not lose any speed f) in the absence of retarding forces, the tendency of the ball is to move forever without slowing down g) we call this property of an object to resist changes in motion inertia

Who is Galileo?

1. Galileo developed an early interest in motion and was soon at odds with his contemporaries, who held to Aristotelian ideas on falling bodies and generally believed that the Sun goes around Earth a) Galileo left Pisa to teach at the University of Padua and became an advocate of the new Copernican theory of the solar system 2. He was the first man to discover mountains on the Moon and to find the moons of Jupiter a) because he published his findings in Italian, the language of the people, instead of in Latin, the language of scholars, and because of the recent invention of the printing press, Galileo's ideas reached a wide readership 3. He soon ran afoul of the Church, and he was warned not to teach or hold to Copernican views a) he restrained himself publicly for nearly 15 years and then defiantly published his observations and conclusions, which were counter to Church doctrine b) The outcome was a trial in which he was found guilty, and he was forced to renounce his discovery that Earth moves c) as he walked out of the court, it is said that he whispered, 'But it moves.' d) by then an old man, broken in health and spirit, Galileo was sentenced to perpetual house arrest e) nevertheless, he completed his studies on motion, and his writings were smuggled out of Italy and published in Holland.

What did Galileo discover about acceleration from inclined planes experiments?

1. Galileo developed the concept of acceleration in his experiments on inclined planes a) his main interest was falling objects, and because he lacked accurate timing devices, he used inclined planes effectively to slow accelerated motion and to investigate it more carefully 2. Galileo found that a ball rolling down an inclined plane picks up the same amount of speed in successive seconds; that is, the ball rolls with unchanging acceleration-constant acceleration a) for example, a ball rolling down a plane inclined at a certain angle might be found to pick up a speed of 2 meters per second for each second it rolls b) this gain per second is its acceleration c) its instantaneous velocity at 1 second intervals, at this acceleration, is then 0,2,4,6,8,10, and so forth, meters per second 3. We can see that the instantaneous speed or velocity of the ball at any given time after being released from rest is simply equal to its acceleration multiplied by the time: VELOCITY ACQUIRED = ACCELERATION X TIME a) if we substitute the acceleration of the ball in this relationship (2 meters per second squared), we can see that, at the end of 1 second, the ball is traveling at 2 meters per second; at the end of 2 seconds, it is traveling at 4 meters per second; at the end of 10 seconds, it is traveling at 20 meters per second, and so on 4. the instantaneous speed or velocity at any time is equal to the acceleration multiplied by the number of seconds it has been accelerating 5. Galileo found that acceleration down each incline was constant for each incline, with greater accelerations for steeper inclines a) the ball attains its maximum acceleration when the incline is tipped vertically b) then it falls with the acceleration of a falling object c) regardless of the weight or size of the object, Galileo discovered that, when air resistance is small enough to be ignored all objects fall with the same unchanging acceleration d) the acceleration due to gravity is 10 m/s each second all the way down

How did Galileo develop his concept of inertia? How was it different than Aristotle's ideas of motion? How did it bring about Newton's laws

1. Galileo was concerned with how things move rather than why they move a) he showed that experiment rather than logic is the best test of knowledge 2. Aristotle was an astute observer of nature, and he dealt with problems around him rather than with abstract cases that did not occur in his environment a) motion always involved a resistive medium such as air or water b) he believed a vacuum to be impossible and therefore did not give serious consideration to motion in the absence of an interacting medium c) that's why it was basic to Aristotle that an object requires a push or pull to keep it moving 3. and it was this basic principle that Galileo rejected when he stated that, if there is no interference with a moving object, it will keep moving in a straight line forever; no push, pull, or force of any kind is necessary 4. Galileo's concept of inertia discredited the Aristotelian theory of motion a) Aristotle did not recognize the idea of inertia because he failed to imagine what motion would be like without friction b) in his experience, all motion was subject to resistance, and he made this fact central to his theory of motion c) Aristotle's failure to recognize friction for what it is-namely, a force like any other-impeded the progress of physics for nearly 2000 years, until the time of Galileo d) an application of Galileo's concept of inertia would show that no force is required to keep Earth moving forward e) the way was open for Issac Newton to synthesize a new vision of the universe 5. in 1642, several months after Galileo died, Issac Newton was born a) by the time Newton was 23, he developed his famous laws of motion, which completed the overthrow of the Aristotelian ideas that had dominated the thinking of the best minds for nearly two millennia b) the first of Newton's law is a restatement of the concept of inertia as proposed earlier by Galileo (Newton's three laws of motion first appeared in one of the most important books of all time, Newton's Principia)

How was Aristotle?

1. Greek philosopher, scientist, and educator, Aristotle was the son of a physician who personally served the king of Macedonia 2. at age 17, Aristotle entered the Academy of Plato, where he worked and studied for 20 years until Plato's death a) he then became the tutor of young Alexander the Great b) eight years later he formed his own school 3. Aristotle's aim was to systematize existing knowledge, just as Euclid had systematized geometry a) Aristotle made critical observations, collected specimens, and gathered together, summarized, and classified almost all existing knowledge of the physical world b) his systematic approach became the method from which Western science later arose 4. After his death, his voluminous notebooks were preserved in caves near his home and were later sold to the library at Alexandria a) scholarly activity ceased in most of Europe through the Dark Ages, and the works of Aristotle were forgotten and lost except in the scholarship that continued in the Byzantine and Islamic empires b) various texts were reintroduced to Europe during the 11th and 12th centuries and translated into Latin c) the Church, the dominant political and cultural force in Western Europe, first prohibits the works of Aristotle but then accepted and incorporated them into Christian doctrine.

What are the units that mass and weight are measured in?

1. In the United States, the quantity of matter in an object is commonly described by the gravitational pull between it and Earth and its weight, usually expressed in points a) in most of the world, however, the measure of matter is commonly expressed in a mass unit, the KILOGRAM b) KILOGRAM: THE FUNDAMENTAL SI UNIT OF MASS; EQUAL TO 1000 GRAMS. ONE KILOGRAM IS VERY NEARLY THE AMOUNT OF MASS IN 1 LITER OF WATER AT 4°C c) at the surface of Earth, a brick with a mass of 1 kilogram weighs 2.2 pounds 2. In metric units, the unit of force is the NEWTON, which is equal to a little less than a quarter-pound (like the weight of a quarter pound hamburger after it is cooked a) NEWTON: THE SI UNIT OF FORCE. ONE NEWTON IS THE FORCE APPLIED TO A 1 KILOGRAM MASS THAT WILL PRODUCE AN ACCELERATION OF 1 METER PER SECOND PER SECOND b) a 1 kilogram brick weighs about 10 newtons (more precisely, 9.8N)

What did Galileo discover in his leaning tower of Pisa experiments?

1. It was Galileo, the foremost scientist of the early 17th century, who gave credence to the Copernican view of a moving Earth a) he accomplished this by discrediting the Aristotelian ideas about motion b) although he was not the first to point out difficulties in Aristotle's views, Galileo was the first to provide conclusive refutation through observation and experiment 2. Galileo easily demolished Aristotle's falling body hypothesis a) Galileo is said to have dropped objects of various weights from the top of the Leaning Tower of Pisa to compare their falls a) Contrary to Aristotle's assertion, Galileo found that a stone twice as heavy as another did not fall twice as fast b) except for the small effect of air resistance, he found that objects of various weights, when released at the same time, fell together and hit the ground at the same time 3. on one occasion, Galileo allegedly attracted a large crowd to witness the dropping of two objects of different weight from the top of the tower a) legend has it that many observers of this demonstration who saw the objects hit the ground together scoffed at the young Galileo and continued to hold fast to their Aristotelian teachings

What was Copernicus's views on Earth's movement?

1. It was in this intellectual climate that the Polish astronomer Nicolaus Copernicus formulated his theory of the moving Earth 2. Copernicus reasoned that the simplest way to account for the observed motions of the Sun, Moon, and planets through the sky was to assume that Earth (and other planets) circles around the Sun. 3. For years he worked without making his thoughts public-for two reasons: a) the first was the fear of persecution; a theory so completely different from common opinion would surely be taken as an attack on established order b) the second reason was that he had grave doubts about it himself; he could not reconcile the idea of a moving Earth with the prevailing ideas of motion 4. finally, in the last days of his life, at the urging of close friends, he sent his De Revolutionibus to the printer a) the first copy of his famous exposition reached him on the day he died-May 24, 1543 5. most of us know about the reaction of the medieval church to the idea that Earth travels around the Sun a) Aristotle's views had become a formidable part of Church doctrine, so to contradict them was to question the Church itself b) for many Church leaders, the ideas of a moving Earth threatened not only their authority but the very foundations of faith and civilization as well c) for better or for worse, this new idea was to overturn their conception of the cosmos-although eventually the Church embraced it

How do you do vector addition?

1. ordinarily, sum just means simple addition: 2 +2 =4 a) with vectors, we must also consider direction 2. with a coordinate system reference, geometry can be used to add the vectors a) to add vectors, we arrange them "head to tail" to see where we end up b) so long as we keep the same size and orientation, we can move vectors to any location without changing their fundamental properties

What is the difference between mass and weight?

1. MASS: THE QUANTITY OF MATTER IN AN OBJECT. IT IS ALSO THE MEASURE OF THE INERTIA OR SLUGGISHNESS THAT AN OBJECT EXHIBITS IN RESPONSE TO ANY EFFORT MADE TO START IT, STOP IT, OR CHANGE ITS STATE OF MOTION IN ANY WAY a) Mass = m b) a measure of the inertia of a material object c) independent of gravity, Greater inertia = greater mass d) unit of measurement is the kilogram (kg) e) mass ia a scalar quantity f) our current understanding of mass delves into its source, the recently discovered Higgs boson 2. WEIGHT: USUALLY THE FORCE UPON AN OBJECT DUE TO GRAVITY a) weight = mg b) usually the force on an object due to gravity c) scientific unit of force is the newton (N) d) unit is also the pound (lb) e) weight is a vector quantity. it can sometimes be referred to as force of gravity f) force of gravity (Fg or w) is equation to mass x acceleration due to gravity or Fg=mg g) we say usually in the definition of weight because an object can have weight when gravity is not a factor, such as occurs in a rotating space station 3. in any event, near Earth's surface and in the absence of acceleration, weight and mass are directly proportional to each other a) the weight of an object of mass m due to gravity equals mg where g is the constant of proportionality and has the value 10 N/kg (more precisely 9.8 N/kg) b) equivalently, g is the acceleration due to gravity, 10m/s² (the unit N/kg is equivalent to m/s² c) the direct proportion of mass to weight tells us that if the mass of an object is doubled, its weight is also doubled; if the mass is halved, the weight is halved d) because of this, mass and weight are often interchanged e) also, mass and weight are sometimes confused because it is customary to measure the quantity of matter in things (mass) by their gravitational attraction to Earth (weight) f) but mass is more fundamental than weight; it is a fundamental quantity that completely escapes the notice of most people 4. There are times when weight corresponds to our unconscious notion of inertia a) for example, if you are trying to determine which of two small objects is the heavier one, you might shake them back and forth in your hands or move them in some way instead of lifting them b) in doing so, you are judging which of the two is more difficult to get moving, feeling which of the two is more resistant to a change in motion c) you are really comparing the inertias of the objects-their masses

How is motion of objects described?

1. Motion of objects is always described as RELATIVE to something else 2. For example: a) you walk on the road relative to Earth, but Earth is moving relative to the Sun b) So your motion relative to the Sun is different from your motion relative to Earth 3. Everything moves-even things that appear to be at rest a) if you walk down the aisle of a moving bus, your speed relative to the floor of the bus is likely quite different from your speed relative to the road b) when we say a racing car reaches a speed of 300 kilometers per hour, we mean relative to the track 4. Unless stated otherwise, when we discuss the speeds of things in our environment, we mean relative to the surface of Earth a) motion is relative

What units are legitimate for measuring speed?

1. any combination of distance and time units is legitimate for measuring speed a) for motor vehicles (or long distances), the units kilometers per hour (km/h) and miles per hour (mi/h or mph) are commonly used b) for shorter distances, meters per second (m/s) is more useful 2. the slash symbol (/) is read as per and means "divided by"

what is force and friction dependent on?

1. depends on the kinds of material and how much they are pressed together 2. is due to tiny surface bumps and to "stickiness" of the atoms on a material's surface 3. example: friction between a crate on a smooth wooden floor is less than that on a rough floor

what are directly proportional and inversely proportional equations?

1. directly proportional: straight line, acceleration increases equally 2. inversely proportional: mass increases as acceleration decreases a) the line is weird curve

Why do many objects fall with unequal accelerations?

1. it is a common observation that many objects fall with unequal accelerations a) a leaf, a feather, a sheet of paper may flutter to the ground slowly 2. the fact that air resistance is responsible for these different accelerations can be shown very nicely with a closed glass tube containing light and heavy objects-a feather and a coin for example a) in the presence of air, the feather and coin fall with quite different accelerations b) but, if the air in the tube is removed by a vacuum pump and the tube is quickly inverted, the feather and coin fall with the same acceleration c) although air resistance appreciably alters the motion of things like falling feathers, the motion of heavier objects like stones and baseballs at ordinary low speeds is not appreciably affected by the air d) the relationships v=gt and d= 1/2gt² can be used to obtain a very good approximation for most objects falling in air from an initial position of rest

How is motion affected by an incline?

1. motion increases as the inclination increases 2. acceleration due to gravity = free fall a) acceleration depends on the inclination of the plane b) acceleration increases with the increase of the incline 3. Angle of inclination θ: 0° a) sinθ: 0 b) acceleration (a=gsinθ) in m/s²: 0 c) no acceleration because there is no angle. it is just a horizontal line 4. Angle of inclination θ: 30° a) sinθ: 1/2 b) acceleration (a=gsinθ) in m/s²: g/2 = 4.9 5. Angle of inclination θ: 45° a) sinθ: 1/square root of 2 b) acceleration (a=gsinθ) in m/s²: g/square root of 2 = 6.93 6. Angle of inclination θ: 60° a) sinθ: square root of 3/2 b) acceleration (a=gsinθ) in m/s²: square root of 3g/2=8.49 7. Angle of inclination θ: 90° a) sinθ: 1 b) acceleration (a=gsinθ) in m/s²: g=9.8 c) 90° is a free fall and at the maximum accretion that something can have.

What is the difference between speed or velocity and distance of falling objects?

1. much of the confusion that arises in analyzing the motion of falling objects comes about because it is easy to get "how fast" mixed up with "how far" a) when we wish to specify how fast something is falling, we are talking about speed or velocity, which is expressed as v=gt b) when we wish to specify how far something falls, we are talking about distance, which is expressed as d= 1/2gt² c) it is important to understand that speed or velocity (how fast) and distance (how far) are entirely different from each other 2. a most confusing concept is "how quickly does how fast change"- acceleration? a) what makes acceleration so complex is that it is A RATE OF A RATE b) it is often confused with velocity, which is itself a rate (the rate of change of position) c) acceleration is not velocity, nor is it even a change in velocity d) it is important to understand that acceleration is the rate at which velocity itself changes

What does the acceleration imparted on an object depend on? How is acceleration impacted by mass

1. the acceleration imparted to an object depends not only on applied forces and friction forces, but also on the inertia of the object, its resistance to change in its motion a) how much inertia an object possesses depends on the amount of matter in the object-the more matter, the more inertia 2. the amount of acceleration depends not only on the force but also on the mass being pushed a) the same force applied to twice the mass produces half the acceleration; for three times the mass, one-third the acceleration b) we say that, for a given force, the acceleration produced is inversely proportional to the mass; that is, acceleration ∼ 1/mass c) by inversely we mean that the two values change in opposite ways d) for example, if one value doubles, the other value halves

What does the amount of inertia possessed on an object depend on?

1. the amount of inertia possessed by an object depends on its mass (m) 2. mass is measured in kilogram (kg) 3. greater mass = greater inertia 4. smaller mass = smaller inertia 5. mass is the measure of inertia of an object

What is the distance covered by an accelerating object?

1. the distance covered by an accelerating object starting from rest is: distance = (1/2) x acceleration x time x time a) d=1/2at² b) d=1/2gt²: free fall when it is acceleration due to gravity c) the acceleration would be negative because gravity is pulling is down 2. how far an object falls is entirely different from how fast it falls a) with his inclined planes, Galileo found that the distance a uniformly accelerating object travels is proportional to the SQUARE OF THE TIME b) the distance traveled by a uniformly accelerating object starting from rest is: distance traveled (1/2) acceleration x time x time c) this relationship applies to the distance something falls d) we can express it, for the case of a freely falling object, in shorthand notation as d= 1/2gt² in which d is the distance something falls when the time of fall in seconds is substituted for t and squared 3. NOTE THAT AN OBJECT FALLS A DISTANCE OF ONLY 5 METERS DURING THE FIRST SECOND OF FALL, ALTHOUGH ITS SPEED IS THEN 10 METERS PER SECOND a) this may be confusing; we may think that the object should fall a distance of 10 meters b) but for it to fall 10 meters in its first second fall, it would have to fall at an average speed of 10 meters per second for the entire second c) it starts its fall at 0 meters per second and its speed is 10 meters per second only in the last instant of the 1 second interval d) its average speed during this interval is the average of its initial and final speeds, 0 and 10 meters per second e) to find the average value of these or any two numbers, we simply add the two numbers and divide the total by 2 f) this equals 5 meters per second, which, over a time interval of 1 second, gives a distance of 5 meters g) as the object continues to fall in successive seconds, it will fall through ever increasing distances because its speed is continuously increasing

What is the speed and velocity of an object under free fall?

1. the velocity acquired by an object starting from rest is: velocity = acceleration x time or v=gt a) the instantaneous speed or velocity of an object falling from rest is consistent with the equation that Galileo deduced with his inclined planes: velocity acquired = acceleration x time b) the instantaneous velocity v of an object falling from rest after a time t can be expressed in shorthand notation as v=gt c) note that the instantaneous velocity or speed in meters per second is simply the acceleration g=10 m/s² multiplied by the time t in seconds 2. so under free fall, when acceleration is 9.8 m/s², the speed is: a) 9.8 m/s after 1s b) 19.6 m/s after 2 s c) 29.4 m/s after 3 s and so on 3. If the object is going up, the direction is positive. if the object is going down, the direction is negative 4. the velocity increases by an equal amount, but the distance will not because the velocity is linear

What are the properties of vectors and how are they displayed?

1. two vectors are equal if they have the same magnitude and direction a) this is true regardless of the starting points of the vectors 2. displacement is the straight line connection from the initial to the final position and would be written as →S = 200ft, northeast a) the magnitude of the displacement is S=|S|= 200ft, the distance between his initial and final points

A hiker's displacement is 4 miles to the east, then 3 miles to the north. How do you solve it? Solve it?

1. vector →C is the net displacement: →C = →A + →B a) because →A and →B are at right angles, the magnitude of →C is given by the Pythagorean theorem: C=square root of A² + B² = square root of (4mi)² + (3mi)² = 5mi b) to describe the direction of →C we find the angle: θ= tan⁻¹(B/A) = tan⁻¹(3mi/4mi) = 37° c) altogether, the hiker's net displacement is →C = →A + →B = (5mi, 37° north of east)

What is the difference between acceleration, velocity, and speed?

1. we accelerate whenever we move in a curved path, even if we are moving at constant speed, because our direction is changing every instant-hence, our velocity is changing a) we distinguish speed and velocity for this reason and define acceleration as the rate at which velocity changes, thereby encompassing changes both in speed and in direction 2. anyone who has stood in a crowded bus has experienced the difference between velocity and acceleration a) except for the effects of a bumpy road, you can stand with no extra effort inside a bus that moves at constant velocity, no matter how fast it is going b) you can flip a coin an catch it exactly as if the bus were at rest c) it is only when the bus accelerates-speeds up, slows down, or turns-that you experience difficulty standing 3. in much of this book, we will be concerned only with motion along a straight line a) when one way straight line motion is being considered, it is common to use the terms speed and velocity interchangeably b) when direction doesn't change, acceleration may be expressed as the rate at which speed changes c) acceleration (along a straight line) = change in speed/time interval

How does the idea of inertia support the concept that the earth moves?

1. when Copernicus announced the idea of a moving Earth in the 16th century, the concept of inertia was not understood a) there was much arguing and debate about whether or not earth moved b) the amount of force required to keep Earth moving was beyond imagination 2. people often counter argued Copernicus's theory by saying that the speed at which Earth would have to move in order to circle the Sun in one year (30 kilometers per second), would make it impossible for objects to remain at rest on earth. (birds can't catch worms cause the worm would be sweated away from the earth) 3. To refute this argument, you need to invoke the idea of inertia a) not only is Earth moving at 30 kilometers per second but so are the tree, the branch of the tree, the bird on the branch, the worm below, and even the air in between b) all are moving at 30 kilometers per second c) things in motion remain in motion if no unbalanced forces are acting upon them d) so, when the bird drops from the branch, its initial sideways motion of 30 kilometer per second remains unchanged e) it catches the worm, quite unaffected by the motion of its total environment f) the 30 kilometers per second is the speed of the Earth relative to the Sun, not the speed of you relative to any object 3. People 400 years ago had difficulty with ideas like these, not only because they failed to acknowledge the concept of inertia but because they were not accustomed to moving in high speed vehicles a) slow, bumpy rides in horse drawn carriages did not lend themselves to experiments that would reveal the effect of inertia b) today we flip a coin in a high speed car, bus, or plane and we catch the vertically moving coin as we would if the vehicle were at rest c) we see evidence for the law of inertia when the horizontal motion of the coin before, during, and after the catch is the same d) the coin keeps up with us e) the vertical force of gravity affects only the vertical motion of the coin 4. our notions of motion today are very different from those of our ancestors a) Aristotle did not recognize the idea of inertia because he did not see that all moving things follow the same rules b) he imagined that the rules for motions in then heavens were very difficult from the rules for motion on Earth c) he saw vertical motion as natural but horizontal motion as unnatural, requiring a sustained force d) Galileo and Newton, on the other hand, saw that all moving things follow the same rules e) to them, moving things require no force to keep moving if there are no opposing forces, such as friction f) we can only wonder how differently science might have progressed if Aristotle had recognized the unity of all kinds of motion

What is hang time

1. when you jump, you will remain in the air for a second before you fall down 2. hang time is how long you remain in the air. it depends on your speed and acceleration due to gravity. Increase speed to increase your hang time 3. some athletes and dancers have great jumping ability a) leaping straight up, they seem to "hang in the air," defying gravity b) ask your friends to estimate the "hang time" of the great jumpers-the time a jumper is airborne with feet off the ground c) they may say 2 or 3 seconds d) but surprisingly, the hang time of the greatest jumpers is almost always less than 1 second e) a longer time is one of many illusions we have about nature 4. a related illusion is the vertical height a human can jump a) most your classmates probably cannot jump higher than 0.5 meter b) they can step over a 0.5 meter fence, but, in doing so, their body rises only slightly c) the height of the barrier is different from the height a jumper's "center of gravity" rises d) many people can leap over a 1 meter fence, but only rarely does anybody raise the "center of gravity" of their body 1 meter e) even the greatest basketball starts can't raise their body 1.25 meters high, although they can easily reach considerably above the more than 3 meter high basket 5. jumping ability is best measured by a standing vertical jump a) when you leap upward, jumping force is applied only while your feet make contact with the ground b) the greater the force, the greater your launch speed and the higher the jump c) as soon as your feet leave the ground, your upward speed immediately decreases at the steady rate of g-10 m/s² d) at the top of your jump, your upward speed decreases to zero e) then you begin to fall, gaining speed at exactly the same rate g f) if you land as you took off, upright with legs extended,d then time rising equals time falling g) HANG TIME IS THE SUM OF RISING AND FALLING TIMES h) while you are airborne, no amount of leg or arm pumping or other bodily motions can change your hang time 6. If we know vertical height d, we can rearrange the distance formula to read: t = the square root of 2d/g 7. no basketball player is known to have attained a standing vertical jump of 1.25 meters a) setting d as 1.25 meters and using them ore precise value of 9.8 m/s² for g, we solve for t, half the hang time, and get t= square root of 2(1.25m)/9.8m/s² = 0.50s b) double this because this is the time for one way of an up and down round trip and we get a record breaking hang time of 1 second 8. Hang time of a running jump only depends on the jumper's vertical speed at launch a) while airborne, the jumper's horizontal speed remains constant and only the vertical speed undergoes acceleration

What is acceleration and what is its formula?

ACCELERATION: THE RATE AT WHICH AN OBJECT'S VELOCITY CHANGES WITH TIME; THE CHANGE IN VELOCITY MAY BE IN MAGNITUDE (SPEED), OR DIRECTION, OR BOTH a) we can change the velocity of something by changing its speed, by changing its direction, or by changing both its speed and its direction b) how quickly and in what direction velocity changes is acceleration 1. acceleration = change in velocity/time interval a) units m/s² b) a =∆v/∆t c) →a =→∆v/∆t d) change in velocity = final velocity (vf) - initial velocity (vi) 2. We are familiar with acceleration in an automobile a) when the driver depresses the gas pedal (appropriately called the accelerator), the passengers experience acceleration (or pickup as it is sometimes called) as they are pressed against their seats 3. THE KEY IDEA THAT DEFINES ACCELERATION IS CHANGE a) suppose we are driving an in 1 second we steadily increase our velocity from 30 kilometers per hour to 35 kilometers per hour, and then to 40 kilometers per hour in the next second, to 45 in the next second, and so on b) we change our velocity by 5 kilometers per hour each second c) this change in velocity is what we mean by acceleration d) acceleration = change of velocity/time interval = 5km/h/1s = 5km/h x s e) in this case, the acceleration is 5 kilometers per hour second, in the forward direction 4. NOTE THAT A UNIT FOR TIME ENTERS TWICE: once for the unit of velocity and again for the time interval in which the velocity is changing a) ALSO NOTE THAT ACCELERATION IS NOT JUST THE TOTAL CHANGE IN VELOCITY; IT IS THE TIME RATE OF CHANGE OR CHANGE PER SECOND IN VELOCITY 5. The term acceleration applies to decreases as well as to increases in velocity a) we say the brakes for a car, for example, produce large retarding accelerations; that is, there is a large decrease per second in the velocity of the car b) we often call this DECELERATION c) we experience deceleration when the driver of a bus or car applies the brakes and we tend to lurch forward (car has three controls that change velocity-the gas pedal, the brakes, and the steering wheel)

What is average speed?

AVERAGE SPEED: path distance divided by time interval 1. In planning a trip by car, the driver often wants to know the time of travel a) the driver is concerned with the average speed for the trip 2. average speed can be calculated using this formula: average speed = total distance covered/time interval 3. we see that, when a distance in kilometers (km) is divided by a time in hours (h), the answer is in kilometers per hour (km/h) 4. since average speed is the distance traveled divided by the total time of travel, it doesn't indicate the different speeds and variations that ay have taken place during shorter time intervals a) on most trips, we experience a variety of speeds, so the average speed is often quite different from the instantaneous speed at any particular moment b) if we know average speed and time of travel, distance traveled is easy to find c) a simple rearrangement of our definition gives: distance travelled = average speed/time of travel

What is Newton's first law of motion?

EVERY OBJECT HAS A TENDENCY TO REMAIN IN ITS STATE OF REST OR OF UNIFORM MOTION IN A STRAIGHT LINE UNLESS ACTED ON BY A UNBALANCED FORCE /EVERY OBJECT CONTINUES IN A STATE OF REST OR OF UNIFORM SPEED IN A STRAIGHT LINE UNLESS ACTED ON BY A NONZERO NET FORCE a) also known as the law of inertia b) Aristotle's ideas that a moving object must be propelled by a steady force was completely turned around by Galileo, who stated that, in the absence of a force, a moving object will continue moving c) the tendency of things to resist changes in motion was what Galileo called inertia d) Newton refined Galileo's idea and made it his first law, appropriately called the law of inertia 1. we say an object moves if the object changes it position with respect to some reference frame 2. everything in the universe is in constant motion 3. Uniform motion: velocity is constant (speed and direction are constant) a) unbalanced force: add up all of the forces acting on the object to find its resultant. If the number of forces do not cancel out to have a net force of 0 then it is an unbalanced force. b) if a balanced force occurs, it will move with a constant velocity and net force will be zero. (same if its at rest) 4. The key word in this law is continues: an object continues to do whatever it happens to be doing unless a force is exerted upon it a) if it is at rest, it continues in a state of rest b) this is nicely demonstrated when a tablecloth is skillfully whipped from under dishes on a tabletop, leading the dishes in their initial state of rest c) we stress that this property of objects to resist changes in motion is what we call inertia d) if an object is moving, it continues to move without turning or changing its speed e) this is evident in space probes that continuously move in outer space f) changes in motion must be imposed against the tendency of an object to retain its state of motion g) in the absence of net forces, a moving object tends to move along a straight line path indefinitely

What is force?

FORCE: ANY PUSH OR PULL ON AN OBJECT; A VECTOR QUANTITY MEASURED IN NEWTONS. UNBALANCED FORCE CHANGES AN OBJECT'S MOTION 1. to change an object's state of rest or of uniform motion in a straight line we need a force 2. force is measured in Newton (N) a) 1 N/kg = 1 kg x m/s² 3. force is a vector quantity: it has magnitude as well as direction 4. we need to use vector addition to add two vectors 5. Changes in motion are produced by a force or combination of forces (refer to to changes in motion as acceleration) 6. its source may be gravitational, electrical, magnetic, or simply muscular effect

What is free fall?

FREE FALL: MOTION UNDER THE INFLUENCE OF GRAVITY ONLY a) falling under the influence of gravity only with no air resistance 1. things fall because of the force of gravity a) when a falling object is free of all restraints-no friction, with the air or otherwise-and falls under the influence of gravity alone, the object is in a state of free fall 2. freely falling objects on Earth accelerate at the rate of 9.8 m/s∙s, that is: g=9.8 m/s² a) can round up to g=10 m/s² b) maximum rate of any falling object is g=9.8 m/s² 3. DURING EACH SECOND OF FALL, THE OBJECT GAINS A SPEED OF 10 METERS PER SECOND a) this gain per second is acceleration b) free fall acceleration is approximately equal to 10 meters per second each second or, in shorthand notation, 10 m/s² c) note that the unit of time, the second, enters twice-once for the unit of speed and again for the time interval during which the speed changes 4. In the case of freely falling objects, it is customary to use the letter g to represent the acceleration (because the acceleration is due to GRAVITY) a) the value of g is very different on the surface of the Moon and on the surfaces of other planets b) here on earth, g varies slightly in different locations, with an average value equal to 9.8 meters per second each second, or, in shorter notation, 9.8 m/s² c) we round this off to 10 m/s² in our present discussion and to establish the ideas involved more clearly; multiples of 10 are more obvious than multiples of 9.8 d) where accuracy is important, the value of 9.8 m/s² should be used 5. Free fall acceleration is clearer when we consider a falling object equipped with a speedometer a) suppose rock is dropped from a high cliff and you witness it with a telescope b) if you focus the telescope on the speedometer, you'd note increasing speed as time progresses by 10 m/s each succeeding second

How does mass react to acceleration?

Mass resists acceleration 1. the same force applied to: a) twice the mass produces half the acceleration b) 3 times the mass, produces 1/3 the acceleration 2. acceleration is inversely proportional to mass or acceleration ∼ 1/mass

What is Aristotle's classification of motion?

NATURAL MOTION: EVERY OBJECT IN THE UNIVERSE HAS A PROPER PLACE DETERMINED BY A COMBINATION OF FOUR ELEMENTS: EARTH, WATER, AIR, AND FIRE 1. any object not in its proper place will strive to get there 2. Examples: a) stones fall: being of earth, an unsupported lump of clay will fall to the ground b) puffs of smoke rise: being of air, an unimpeded puff of smoke will rise c) being a mixture of earth and air but predominantly earth, a feather will fall to the ground, but not as rapidly as a lump of clay 3. Straight up or straight down for all things on earth a) Aristotle stated that heavier objects would strive harder and argued that objects should fall at speeds proportional to their weights: the heavier the object, the faster it should fall b) natural motion could be either straight up or straight down, as in the case of all things on earth 4. beyond Earth, motion is circular (celestial objects) a) unlike up and down motion, circular motion has no beginning or end, repeating itself without deviation b) Aristotle believed that different rules apply to the heavens and asserted that celestial bodies are perfect spheres made of a perfect and unchanging substance, which he called quintessence (the only celestial object with any detectable variation on its face was the moon. medieval christians, still under the sway of Aristotle's teaching, ignorantly explained that lunar imperfections were due to the closeness of the moon and the contamination by human corruption on Earth) 5. Example: the sun and moon continually circle Earth VIOLENT MOTION: imposed motion that resulted from pushing or pulling forces 1. produced by external pushes or pulls on objects 2. Example: a) wind imposes motion on ships b) a person pushing a cart or lifting a heavy weight imposed motion c) someone hurling a stone or winning a tug of war imposed motion d) floodwaters imposed motion on boulders and tree trunks 3. the essential thing about violent motion was that it was externally caused and was imparted to objects; they moved not of themselves, not by their "nature" but because of pushes or pulls 4. the concept of violent motion had its difficulties because the pushes and pulls responsible for it were not always evident a) for example, a bowstring moved an arrow until the arrow left the bow; after that, further explanation of the arrow's motion seemed to require some other pushing agent b) Aristotle imagined, therefore, that a parting of the air by the moving arrow resulted in a squeezing effect on the rear of the arrow as the air rushed back to prevent a vacuum from forming c) the arrow was propelled through the air as a bar of soap is propelled in the bathtub when you squeeze one end of it

What is a net force?

NET FORCE: THE COMBINATION OF ALL THE FORCES THAT ACT ON AN OBJECT 1. when several forces are exerted on an object, they combine to form a NET FORCE given by the vector sum of all the forces: →Feet = ∑(N on top, I=1 on bottom)→F₁ = →F₁ + →F₂ +....→FN 2. if a box is pulled by two ropes, the net force of the box is the arrow pointing in the middle of the parallelogram 3. An example is Nellie Newton hanging from a rope (picture in notes) a) there are three forces acting on Nellie; 1) her weight, mg 2) a tension in the left hadn't side of the rope 3) and a tension in the right hand side of the rope b) because of the different angles, different rope tensions will occur in each side c) nellie hangs in equilibrium, so her weight is supported by two rope tensions, adding vectorially to be equal and opposite in her weight d) the parallelogram rule shows that the tension in the right hand is greater than the tension in the left hand side of the rope e) if you measure the vectors, you'll see that the tension in the right rope is about twice the tension in the left rope f) both rope tensions combine to support Nellie's weight 4. For example, if you and a friend pull in the same direction with equal forces on an object, the forces combine to produce a net force twice as great as your single force a) if you both pull with equal forces in opposite directions, the net force is zero b) the equal but oppositely directed forces cancel each other c) one of the forces can be considered to be the negative of the other, and they add algebraically to zero, with a resulting net force of zero

What is Newton's second law of motion?

Newton's second law relates acceleration and force: THE ACCELERATION PRODUCED BY A NET FORCE ON AN OBJECT IS DIRECTLY PROPORTIONAL TO THE NET FORCE, IS IN THE SAME DIRECTION AS THE NET FORCE, AND IS INVERSELY PROPORTIONAL TO THE MASS OF THE OBJECT 1. In equation form: acceleration = net force/ mass or a = F/m a) also can have →P which is linear moment (mass x velocity) in kg x m/s. this can be the final linear moment and it can also have an initial linear moment 2. if net force acting on object is doubled, the object's acceleration will be doubled a) F=ma 3. if mass of object is doubled, the object's acceleration will be halved 4. Acceleration is directly proportional to net force a) to increase the acceleration of an object, increase the net force acting on it b) acceleration ∞ net force or a∞ F c) acceleration is directly proportional to net force and inversely proportional to mass

What is a resultant?

Resultant: the sum of two or more vectors/THE NET RESULT OF A COMBINATION OF TWO OR MORE VECTORS 1. for vectors in the same direction, add arithmetically 2. for vectors in opposite directions, subtract arithmetically 3. two vectors that don't act in the same or opposite direction: use parallelogram rule a) construct a parallelogram in which the two vectors are adjacent sides-the diagonal of the parallelogram shows the result b) in the special case oft vectors that are equal in magnitude and perpendicular to each other, the parallelogram is a square c) since for any square the length of a diagonal is the square root of 2 or 1.41, times one of the sizes, the result is the square root of 2 times one of the vectors d) for example, the resultant of two equal vectors of magnitude 100 acting at a right angle to each other is 141 4. two vectors at right angles to each other: use Pythagorean theorem

What is support force?

SUPPORT FORCE: A FORCE THAT SUPPORTS AN OBJECT ON A SURFACE 1. also called the normal force (because it acts perpendicular, or normal, to the surface) 2. example: a book on a table compresses atoms in the table, and the compressed atoms produce the support force a) the book is in equilibrium because it is lying in rest. b) one force that is acting on the book is the downward force due to gravity-the weight of the book c) the table exerts an upward support force that is opposite to the force of Earth's gravity d) this upward support force, often called the NORMAL FORCE, must equal the weight of the book e) if we call the upward force positive, then the downward weight is negative, and the two add to zero f) the net force on the book is zero or ∑F=0 g) the book lying on the table compresses atoms in the table, which behave like microscopic springs h) the weight of the book squeezes downward on the atoms, and they squeeze upward on the book i) in this way, the compressed atoms produce the support force 3. when you push down on a spring, the spring pushes back up on you 4. When you step on a bathroom scale, two forces act on the scale a) one is your downward push on the scale-the result of gravity pulling on you-and the other is the upward support force of the floor b) these forces squeeze a mechanism (in effect, a spring) within the scale that is calibrated to show the magnitude of the support force c) the force with which you push down on the scale is your weight, which has the same magnitude as the upward support force d) when you are in equilibrium your weight equals the force of gravity acting on you

What is velocity?

VELOCITY: THE SPEED OF AN OBJECT AND ITS DIRECTION OF MOTION; A VECTOR QUANTITY 1. a description of both: a) the instantaneous speed of the object b) the direction of travel 2. velocity is a vector quantity. It has: a) magnitude (speed) and direction b) velocity is "directed" speed 3. Velocity combines the ideas of speed and direction of motion a) for example, if a car travels at 60 km/h, we know its speed b) but if we say the car moves at 60km/h to the north, we specify its velocity c) speed is a description of how fast; velocity is how fast and in what direction 4. There are two types of velocity: a) constant velocity. b) changing velocity

when does the proportion form of Newton's second law take the form of an equation? a) when vector quantities are specified b) when units of newtons and kilograms are used for force and mass c) when a proportionality constant is introduced d) when force and mass are clearly related

b) when units of newtons and kilograms are used for force and mass

What did Galileo demonstrate in his Leaning Tower of Pisa experiment? a) he demonstrated that light and heavy objects gain the same amount of speed when falling b) he demonstrated that the forces on falling objects are the same c) he demonstrated that air resistance has no effect on falling objects d) he demonstrated that heavy objects fall faster than light objects

a) he demonstrated that light and heavy objects gain the same amount of speed when falling

What did Copernicus say about the motion of the Sun? a) the sun is stationary and Earth circles it b) The Sun circles Earth each 365 days c) the Sun rises and falls each 24 hours d) The Sun circles Earth each 24 hours

a) the sun is stationary and Earth circles it

What is a vector? What are the types of vector quantities? How are vectors represented?

an arrow whose length represents the magnitude of a quantity and whose direction represents the direction of the quantity a) used to displace net force 1. SCALAR QUANTITY: a quantity that is fully described by a single number (ie: mass, temperature, volume) a) does not have direction and does not have an arrow b) scalar quantity: has magnitude. c) example: mass, volume, speed d) SCALAR QUANTITY: A QUANTITY IN PHYSICS, SUCH AS MASS, VOLUME, AND TIME, THAT CAN BE COMPLETELY SPECIFIED BY ITS MAGNITUDE AND HAS NO DIRECTION 2. VECTOR QUANTITY: a quantity having both a magnitude (ex: 10 m/s) and a direction (ex: due north) a) needs both magnitude and direction. has to have an arrow b) a quantity whose description requires both magnitude (how much) and direction (which way) c) can be represented by arrows drawn to scale, called vectors d) length of arrow represents magnitude and arrowhead shows direction d) VECTOR QUANTITY: A QUANTITY IN PHYSICS THAT HAS BOTH MAGNITUDE AND DIRECTION. EXAMPLES ARE FORCE, VELOCITY, ACCELERATION, TORQUE, AND ELECTRIC AND MAGNETIC FIELDS 3. the geometric representation of a vector is an arrow with the tail of the arrow placed at the point where the measurement is made a) we label vectors by drawing a small arrow over the letter that represents the vector b) →r for position, →v for velocity, →a for acceleration 4. the vector is drawn across the page, but it represents the particles velocity at this one point (bullet pointed) a) under the arrow is the name of the vector written with an arrow above the letter b) the direction of the vector is found in an arrow in front of the main arrow, pointing the direction (due north, west, south, east) c) magnitude of the vector is written above an arrow with two arrow heads as v=5 m/s

What is the net force on a crate sliding at an unchanging speed when pushed with a steady force of 75 N? a) 75 N b) zero c) somewhat less than 75 N d) slightly more than 75 N

b) zero

The direction of the force of friction on a sliding crate is_______ a) non directional b) opposite to the direction of sliding c) in the same direction as the force that produces sliding d) usually at right angles to the force that produces sliding

b) opposite to the direction of sliding

which depends on gravity? a) mass b) weight c) both of them d) neither of them

b) weight

What two classes of motion did Aristotle advocate? a) propelled motion and passive motion b) earthly motion and heavenly motion c) natural motion and violent motion d) vertical motion and horizontal motion

c) natural motion and violent motion

Galileo's definition of speed was a breakthrough because he is acknowledge to be the first to consider______________ a) direction b) mathematics c) time d) distance covered

c) time

Whenever a net force acts on an object, there is a change in the object's__________ a) speed b) shape c) velocity d) direction

c) velocity

What was the greatest discovery by Galileo during his inclined plane experiments? a) he discovered that heavy objects roll faster than light objects on an incline b) he discovered that light and heavy objects gain the same speed when rolling on inclines c) he discovered that balls rolling down an incline gain speed and balls rolling up an incline lose speed d) he discovered that a ball rolling down an incline and onto a horizontal surface would roll indefinitely

d) he discovered that a ball rolling down an incline and onto a horizontal surface would roll indefinitely

in considering proportions, acceleration is___________ a) equal to the produce of force and mass b) inversely proportional to mass squared c) directly proportional to mass d) inversely proportional to mass

d) inversely proportional to mass