Basic Physics Exam 1

C3: What is the acceleration of a car moving along a straight road that increases its speed from 0 to 100 km/h in 10 s?

10 km/h·s

C4H: Given the measurements 10 m, 10 m/s, and 10 m/s2, which is a measure of speed, which is a measure of distance, and which is a measure of acceleration?

10 m is distance, 10 m/s is speed, and 10 m/s2 is acceleration

CL5: A soccer player kicks a ball with 1500 N of force. The ball exerts a reaction force against the player's foot of

1500 N

C3: An automobile is accelerating when it is

Both of the above.

C2: What did Galileo discover about moving bodies and force in his experiments with inclined planes?

In the absence of a retarding force, a body will keep moving at a constant speed in a straight line forever.

C4H: Madison tosses a ball straight upward. Anthony drops a ball. Your discussion partner says both balls undergo the same acceleration. What is your response?

In the absence of air resistance both accelerations are g, the same. Their velocities may be in opposite directions, but g is the same for both.

C2: You are riding in a vehicle at a steady speed and toss a coin straight upward. Where will the coin land?

In your hand. Due to the coin's inertia, it continues sideways with the same speed as the vehicle in its up-and-down motion, which is why it lands in your hand.

C2: What is inertia?

Inertia is the tendency of a body to maintain its state of motion in the absence of applied forces.

CH6 Fill in the blanks: Newton's first law is often called the law of ____; Newton's second law is the law of ____; and Newton's third law is the law of ____

Inertia, acceleration, action -reaction

C3: What kind of speed is registered by an automobile speedometer?

Instantaneous speed

C4H: What is the acceleration of the ball when it is moving up, when it is at the maximum height, and when it is moving down? (Note: The acceleration graph is shown in red.)

It is always negative In fact, the acceleration due to gravity is always 10 m/s2 downward. In other words, it is -10 m/s2.

C4H: What is the value of the velocity of the ball when it reaches its maximum height?

It is always zero.

CL6: When a dish falls, will the change in momentum be less if it lands on a carpet than if it lands on a hard floor? (Careful!)

No, both are the same.

CH6 Can you physically touch a person without that person touching you with the same amount of force?

No, when you touch a person, they must touch you with an equal and opposite force

C3: Which of the quantities are scalar quantities and which are vector quantities?

Scalar quantities: Age, Temp. Vector quantities : Acceleration, Force

CH1: What is science?

Science describes the order in nature and the causes of that order. Science is a way of knowing about the world and making sense of it. Science creates testable laws and theories.

C1: Clearly distinguish between science and technology.

Science gathers the knowledge that technology uses for practical purposes.

C1: What test can you perform to increase the chance in your own mind that you are right about a particular idea?

See if you can state the objections of your opponents to their satisfaction.

CH5: Shake something to and fro and you're measuring its what? Lift it against gravity and you're measuring its what?

Shaking measures mass, whereas lifting measures weight.

CH5: Which is normally greater: static friction or sliding friction on the same object?

Static friction is normally greater than dynamic friction.

C3: A different scaffold that weighs 400 N supports two painters, one 500 N and the other 400 N. The reading in the left scale is 800 N. What is the reading in the right-hand scale?

T = 500 N

CH6 Why does a heavy parachutist fall faster than a lighter parachutist who wears a parachute of the same size?

Terminal speed must be higher to make air drag equal the gravity force for a heavier person.

C4H : Based on the experiment that Dr. Hewitt demonstrated in the video, what factors determine whether the air resistance experienced by a falling object will affect the motion of the object?

The area of the object in relation to the weight of the object determines the air resistance the object experiences. Objects having greater area but smaller weight experience greater effect of air resistance.

CH6 If two objects of the same size move through the air at different speeds, which encounters the greater air resistance?

The faster object encounters more air resistance.

CH6 What two principal factors affect the force of air resistance on a falling object?

The force depends mostly on frontal area and speed.

CH5: How does the force of friction for a sliding object vary with speed?

The force of friction is approximately independent of speed.

CH6 You exert a force on a ball when you toss it upward. How long does that force last after the ball leaves your hand?

The force you exert on the ball ceases as soon as contact with your hand ceases.

CH5: As you increase your push on a stationary crate, will friction on the crate increase also?

The friction force increases and is opposite in direction to your push.

CH5: When you push horizontally on a crate that doesn't slide on a level floor, how great is the force of friction on the crate?

The friction force is equal and opposite to your push.

C3: If you push on a crate with a horizontal force of 100 N and it slides at constant velocity, what is the magnitude and direction of the frictional force acting on the crate?

The frictional force on the crate is 100 N opposite the direction of motion.

CH6 How does a helicopter get its lifting force?

The helicopter exerts downward forces on air; the reaction forces of the air on the helicopter are upward and called lift.

C2: What is the net force on a cart that is pulled to the right with 100 pounds of force and to the left with 30 pounds of force?

The net force is 70 pounds to the right.

C3: What is the net force on a bag pulled down by gravity with a force of 18 newtons and pulled upward by a rope with a force of 18 newtons?

The net force is zero newtons.

C3: What is the net force on an object that is pulled with forces of 80 newtons to the right and 80 newtons to the left?

The net force is zero newtons.

C3: What is the net force on an object in either static or dynamic equilibrium?

The net force is zero.

CH6 What is the net force that acts on a 10-N falling object when it encounters 4 N of air resistance? When it encounters10 N of air resistance?

The net forces are 6 N and 0 N, respectively

C2: When Dr. Hewitt pulls the tablecloth, why do the items on the tablecloth do what they do?

Their inertia is sufficient to keep them there.

C3: What is the main difference between speed and velocity?

Velocity includes a direction, but speed does not.

CH6 Weight = mg What is its weight in pounds?

W = 6.4 lb

CL6: A fast-moving car hitting a haystack or hitting a cement wall produces vastly different results. 1. Do both experience the same change in momentum? 2. Do both experience the same impulse? 3. Do both experience the same force?

Yes for 1 and 2

C3: If a car moves with a constant velocity, does it also move with a constant speed?

Yes, because constant velocity requires constant speed in the same direction

C3: A bowling ball at rest is in equilibrium. Is the ball in equilibrium when it moves at constant speed in a straight-line path?

Yes, the bowling ball is in equilibrium because ΣF = 0

CH6 Earth pulls down on you with a gravitational force that you call your weight. Do you pull up on Earth with the same amount of force?

Yes, you pull up on Earth with the same force.

CH5: Once the crate is sliding, how hard do you push to keep it moving at constant velocity?

You push with a force equal to and opposite the dynamic friction force.

C3: When you stand at rest on a bathroom scale, how does your weight compare with the support force from the scale?

Your weight is equal in magnitude and opposite in direction to the support force from the scale.

CH6 Acceleration: a=Fnet/m Calculate the acceleration of a 350000-kg jumbo jet just before takeoff when the thrust on the aircraft is 80000 N .

a = 0.23 m/s2

CH6 If your mass is 90 kg , find your acceleration.

a = 0.49 m/s2

CH6 Consider a mass of 1 kg accelerated 1 m/s2 by a force of 1 N. Consider a mass of 1 kg accelerated 1 m/s2 by a force of 1 N.

a = 1 m/s2

C4H: Select the correct equations that show that the acceleration of a hamster is 5 m/s2 when it increases its velocity from rest to 10 m/s in 2 s.

a=Δv/t=(10m/s)/(2s)=5m/s2

C3: At a particular instant a free-falling object has a speed of 30 m/s. Exactly 1 s later its speed will be

more than 35 m/s.

C3 : A force of gravity pulls downward on a book on a table. What force prevents the book from accelerating downward?

support: Support force (normal force) is an upward force on an object that is opposite to the force of gravity. Example: A book on a table compresses atoms in the table, and the compressed atoms produce the support force.

C4H : If the dart's exit speed is 16.5 m/s and the length of the blowgun is 1.35 m , find the time the dart is in the barrel.

t = 0.164 s

C4H: A dart leaves the barrel of a blowgun at a speed v. The length of the blowgun barrel is L. Assume that the acceleration of the dart in the barrel is uniform. Find a time that the dart moves inside the barrel.

t = 2L/v

C4L: A 5 kg iron ball and a 10 kg iron ball are dropped from rest. For negligible air resistance, the acceleration of the heavier ball will be

the same.

CH6 When a parachutist opens her parachute after reaching terminal speed, in what direction does she accelerate?

up

CH5: A ball is tossed with enough speed straight up so that it is in the air several seconds. Assume upward direction is positive and downward is negative. What is its velocity 1 s before it reaches its highest point?

v = 10.0 m/s

CH5: A ball is tossed with enough speed straight up so that it is in the air several seconds. Assume upward direction is positive and downward is negative What is its velocity 1 s after it reaches its highest point?

v = -10.0 ms

CH5: A ball is tossed with enough speed straight up so that it is in the air several seconds. Assume upward direction is positive and downward is negative. What is the change in its velocity during this 1-s interval?

Δv = -10.0 m/s

CH5: A ball is tossed with enough speed straight up so that it is in the air several seconds. Assume upward direction is positive and downward is negative. What is the change in velocity during the 2-s interval?

Δv = -20.0 m/s

C3: State the equilibrium rule for forces in symbolic notation

ΣF = 0

C3: What is the acceleration of a car that maintains a constant velocity of 100 km/h for 10 s?

0 km/h·s

C3:Two people each pull with 300 N on a rope in a tug of war. What is the net force on the rope?

0N

CH5: What is the weight of a 1-kilogram brick resting on a table?

10 N

CH6 What is the net force that acts on a 1-kg freely falling object?

10 N

CH5: What is the speed over the ground of an airplane flying at 100 km/h relative to the air caught in a 100-km/h right-angle crosswind?

141 km/h

C3: Consider a book that weighs 15 N at rest on a flat table. How many newtons of support force does the table exert on the book?

15 newtons up

C3: If you pull horizontally on a crate with a force of 200 N, it slides across the floor in dynamic equilibrium. How much friction is acting on the crate?

200 N

C3: What is the average speed in kilometers per hour of a horse that gallops a distance of 15 km in a time of 30 min?

30 km/h

C3: How much force is exerted on each person by the rope?

300 N

C2: A cart is pulled to the right with a force of 15 N while being pulled to the left with a force of 20 N. The net force on the cart is

5 N to the left. When you take a 15-N force to the right added to a 20-N force to the left, because the two forces are in opposite directions, they in fact subtract, rather than add. So, the larger 20-N force to the left is cut back by the 15-N force to the right, so that the remaining force, that is, the net force, is only 5 N to the left.

C4L: If a 50-N person is to fall at terminal speed, the air resistance needed is

50 N.

C3: The average speed of driving 30 km in 1 hour is the same as the average speed of driving

60 km in 2 hours.

C3: What is the distance fallen after 4 s for a freely falling object starting from rest?

80 m. Gravite is 10.

C3: if the strong man exerts a downward force of 800 N on the rope, how much upward force is exerted on the block?

800 N

C2: Why do we say that force is a vector quantity?

A force has a magnitude and a direction.

C1: What is the test for whether a hypothesis is scientific or not

A hypothesis is scientific if it is possible to prove it wrong.

C3: When are you most aware of your motion in a moving vehicle: when it is moving steadily in a straight line or when it is accelerating? If you were in a car that moved with absolutely constant velocity (no bumps at all), would you be aware of the motion?

Accelerating. You would not be aware of the motion if you did not look outside the car.

CH5: How does acceleration depend on mass?

Acceleration is inversely proportional to mass.

CH5: State Newton's second law of motion.

Acceleration is proportional to net force and inversely proportional to mass

CH5: How does acceleration depend on the net force?

Acceleration is proportional to the net force

C4H: What is the effect of air resistance on the acceleration of falling objects?

Air resistance decreases the acceleration of falling objects.

C4H: What exactly is meant by a "freely falling" object?

An object in free fall falls under gravity alone with no friction.

C3: What does it mean to say something is in mechanical equilibrium?

An object in mechanical equilibrium experiences a zero net force.

C1: Why is physics considered to be the basic science?

Because all other sciences can be shown to be derived from it.

C4H: When Dr. Hewitt drops a book and a crumpled piece of paper together from the same height, which object hits the ground first, and why?

Both objects hit the ground at the same time because air resistance is negligible.

C2: Consider the video demonstration that you just watched. Which of the following changes would make it more likely for the ball to hit both the white can and the green can?

By Newton's first law, after it has left the circular track, the ball will travel in a straight line until it is subject to a nonzero net force. Thus, the ball can only hit the white can, because that is the only can in the ball's straight-line path.

C3: What two units of measurement are necessary for describing speed?

Distance and time

C2: You push a crate at a steady speed in a straight line. If the friction force is 75 N, how much force must you apply?

Equal to 75 N. The crate is in dynamic equilibrium, so, ∑F=0. Your applied force balances the force of friction.

CH6 If you stand next to a wall on a frictionless skateboard and push the wall with a force of 44 N , how hard does the wall push on you?

F = 44 N

CH5: Does fluid friction vary with speed?

Fluid friction increases as speed increases

C3: What are the units for force?

Force can be expressed in newtons or pounds.

Vectors

Force is a vector quantity A quantity whose description requires both magnitude (how much) and direction (which way). Can be represented by arrows drawn to scale, called vectors Length of arrow represents magnitude and arrowhead shows direction. Examples: force, velocity, acceleration

C4H: What relationship between distance traveled and time did Galileo discover for freely falling objects released from rest?

Galileo discovered that distance increased as the time squared.

C2: What did Galileo discover in his legendary experiment on the Leaning Tower of Pisa?

Galileo found that a heavier stone does not fall significantly faster than a lighter one

Static Equilibrium

If the object is at rest, called Static Equilibrium. Example: hockey puck at rest on slippery ice.

Dynamic Equilibrium

If the object is moving, called Dynamic Equilibrium Example: hock puck sliding at constant speed on slippery ice.

C2: What type of path does a moving object follow in the absence of a force?

It continues to move in a straight line at a constant speed

C4H: What is the distance fallen for a freely falling object 1 s after being dropped from a rest position? What is the distance for a 4-s drop?

It falls 5 m in 1 s and 80 m in 4 s.

C4H: What is the gain in speed per second for a freely falling object?

It gains approximately 10 m/s.

C3: A ball rolling along a floor doesn't continue rolling indefinitely. Is it because it is seeking a place of rest or because some force is acting upon it? If the latter, identify the force.

It is because some force is acting upon it. friction.

CH6 What is the force of friction acting on a shoe at rest on an incline compared with the resultant of the vectors mg and N?

It is equal and opposite.

C4H: When an object is thrown upward, how much speed does it lose each second (ignoring air resistance)?

It loses 10 m/s of speed each second until it reaches the high point, then it gains 10 m/s each second.

C3: If a car is moving at 90 km/h and it rounds a corner, also at 90 km/h, does it maintain a constant speed? A constant velocity?

It maintains a constant speed, but does not maintain a constant velocity.

CH5: Fill in the blanks: The Standard International unit for mass is _____. The Standard International unit for force is _____.

Mass is kilograms; force is newtons

C2: What class of motion did Aristotle attribute to the Moon?

Natural

C2: What state of motion did Aristotle attribute to Earth?

Natural

Natural Motion

Natural Motion: Every object in the universe has a proper place determined by a combination of four elements; earth, water, air and fire.

C2: What two classes of motion did Aristotle advocate?

Natural motion and violent motion

C2: How does Newton's first law of motion relate to Galileo's concept of inertia?

Newton refined Galileo's concept of inertia and made it his first law of motion

C3: Are there any quantities of the following, which are neither vector quantities nor scalar quantities: force, age, acceleration, temperature?

No

CH6 If a motorcycle moves with a constant acceleration, can you conclude that there is no net force acting on it?

No When the motorcycle is moving at constant acceleration there is a net force acting on it.

C1: How does the Moon's diameter compare with the distance between Earth and the Moon?

The Moon's diameter is 1/110 the distance between Earth and the Moon.

CH1: Earth, like everything else illuminated by the Sun, casts a shadow. Why does this shadow taper?

The Sun is much larger than the Earth.

CH6 What is the acceleration of a falling object that has reached its terminal velocity?

The acceleration is 0.

CH5: If the mass of a sliding block is somehow tripled at the same time the net force on it is tripled, how does the resulting acceleration compare with the original acceleration?

The acceleration remains the same.

CH5: If the net force acting on a sliding block is somehow tripled, what happens to the acceleration?

The acceleration triples.

CH6 A boxer can hit a heavy bag with great force. Why can't he hit a piece of tissue paper in midair with the same amount of force?

The boxer can only hit the tissue paper with a force as large as the tissue paper can exert on the boxer, and the low-mass tissue can only exert a weak force.

C2: According to the parallelogram rule, what quantity is represented by the diagonal of a constructed parallelogram?

The diagonal is the resultant, or sum, of two vectors.

C3: Which is more likely to break: a hammock stretched tightly between a pair of trees or one that sags more when you sit on it?

The hammock stretched tightly between a pair of trees is more likely to break. The hammock stretched tightly has more tension in the supporting ropes than one that sags. The tightly stretched ropes are more likely to break.

C4H: In the video, Dr. Hewitt drops a book and a flat piece of paper together from the same height, and one. Why does that object hit the ground first?

The heavier object--the book--hits the ground first because the other, lighter, object is more influenced by air resistance.

CH6: Why doesn't a heavy object accelerate more than a light object when both are freely falling?

The ratio of the weight to mass is the same for all objects in the same locality.

CH6 Consider hitting a baseball with a bat. If we call the force on the bat against the ball the action force, identify the reaction force.

The reaction force is the force by the ball on the bat.

C2: What is the resultant of a pair of one pound forces at right angles to each other?

The resultant is a force of 1.41 pounds in a direction bisecting the 90-degree angle between the two vectors.

C4H: The acceleration of free fall is about 10 m/s2. Why does the seconds unit appear twice?

The second appears once in the denominator of the unit for speed and once for the interval of time.

C4H: What is the speed acquired by a freely falling object 5 s after being dropped from a rest position? What is the speed 6 s after?

The speed is 50 m/s after 5 s and 60 m/s after 6 s

C4H: What relationship did Galileo discover about a ball's acceleration and the steepness of an incline? What acceleration occurs when the plane is vertical?

The steeper the incline, the greater the acceleration. On a vertical incline, the ball is in free fall.

C2: Consider Nellie hanging at rest in Figure 2.11. If the ropes were vertical, with no angle involved, what would be the tension in each rope?

The tension in each rope would be half of the gravity force.

C3: What concept was not understood in the 16th century when people couldn't conceive of a moving Earth?

They did not understand inertia.

C2: Why do the alphabet letters tend to do what they do when you rotate the bowl?

They have inertia−the tendency of an object at rest to stay at rest.

C1: Which of the following are scientific hypotheses?

Tides are caused by the Moon. Chlorophyll makes grass green.

CH6 How many forces are required for an interaction?

Two forces, an action and a reaction, are needed for an interaction.

CH6 Weight = mg Calculate the weight in newtons of a person having a mass of 40 kg .

W = 400 N

CH6 Weight = mg Calculate the weight in newtons of a 2.9-kg melon

W = 29 N

C3: Henry Heavyweight weighs 1450 N and stands on a pair of bathroom scales so that one scale reads twice as much as the other.What are the scale readings?

W1,W2 = 967,483 N

C1: In daily life, people are often praised for maintaining some particular point of view, for the "courage of their convictions." A change of mind is seen as a sign of weakness. How is this different in science?

When a scientist finds evidence that contradicts a law, then the law must be abandoned.

CH5: What is the condition for an object experiencing free fall?

When gravity is the only force acting on an object, it is in free fall

CH6 If a motorcycle moves with a constant velocity, can you conclude that there is no net force acting on it?

Yes Constant velocity means zero acceleration, so yes, no net force acts on the motorcycle.

CH6 Consider a 36-kg block of cement that is pulled sideways with a net force of 160 N . Find its acceleration

a = 4.4 m/s2

CH5: A ball is tossed with enough speed straight up so that it is in the air several seconds. Assume upward direction is positive and downward is negative What is the acceleration of the ball at the moment the ball has zero velocity?

a = -10.0 m/s^2

CH5: A ball is tossed with enough speed straight up so that it is in the air several seconds. Assume upward direction is positive and downward is negative. What is the acceleration of the ball during any of these time intervals?

a = -10.0 m/s^2

CH5: A car takes 6.0 s to go from v=0m/s to v = 20 m/s at constant acceleration. If you wish to find the distance traveled using the equation d=1/2at2, what value should you use for a?

a = 3.3m/s^2

C4H: Jo, with a reaction time of 0.2 second, rides her bike at a speed of 2.0 m/s . She encounters an emergency situation and "immediately" applies her brakes. How far does Jo travel before she actually applies the brakes?

d = 0.40 m

CL6: When the force that produces an impulse acts for twice as much time, the impulse is

doubled.

CL6: When the speed of an object is doubled, its momentum

doubles.

C4L: When Sanjay pushes a refrigerator across a kitchen floor at a constant speed, the force of friction between the refrigerator and the floor is

equal and opposite to Sanjay's push.

C2: When you stand on two bathroom scales with one foot on each scale and with your weight evenly distributed, each scale will read

half your weight. You are at rest, so ∑F=0. Forces from both scales add to cancel your weight. Force from each scale is one-half your weight.

C3: If while riding in a smooth-riding train, you toss a coin upward, the coin will normally land ______.

in your hand

C4L: As the skydiver falls faster and faster through the air, air resistance

increases

C4L: When Sanjay pushes a refrigerator across a kitchen floor at an increasing speed, the amount of friction between the refrigerator and the floor is

less than Sanjay's push.

CH6 Weight = mg Susie Small finds that she weighs 300 N . Calculate her mass.

m = 30 kg

CL5: When a cannon is fired, the accelerations of the cannon and cannonball are different because the

masses are different.

CL6: A moving object has

momentum. energy. speed.

CH5: The direction of the force of friction on a sliding crate is _______.

opposite to the direction of sliding

CH5: A ball is tossed with enough speed straight up so that it is in the air several seconds. Assume upward direction is positive and downward is negative What is the velocity of the ball when it reaches its highest point?

v = 0 m/s

CH5: An airplane with an airspeed of 108 km/h encounters a 45-km/h crosswind. Select the correct equations that show that the plane's groundspeed is 117 km/h .

v=√v2/1+v2/2 =√((108km/h)^2+(45km/h)^2)= 117km/h

CH5: A rowboat heads directly across a river at a speed of 3 m/s. Select the correct equations that show that if the river flows at 4 m/s, the speed of the boat relative to the riverbank is 5 m/s.

v=√v2/1+v2/2=√((3m/s)^2+(4m/s)^2) = 5m/s

CH5: Vertically falling rain makes slanted streaks on the side windows of a moving automobile. If the streaks make an angle of 45∘ with vertical, calculate the ratio of the speed of the automobile to the speed of the falling rain.

vcar/vrain = 1.0

C2: The equilibrium rule, ∑F=0, applies to

vector quantities. Vector addition accounts for + and - quantities. So, two vectors in opposite directions can add to zero.

CL5: When you step off a curb, Earth pulls you downward. The reaction to this force is

you pulling Earth upward