physics
When representing velocity as a vector,
-the direction of the arrow shows the direction of motion. -the length of the arrow represents the speed. -the length of the arrow is drawn to a suitable scale.
When an object reaches terminal velocity its acceleration is
0 m/s/s
An apple weighs 1 N. The net force on the apple when it is in free fall is
1 N
the vertical height attained by a basketball player who achieves a hang time of a full one second is about
1.2 m
Suppose the force of friction on a sliding object is 10 N. The force needed to maintain a constant velocity is
10 N
A ball is thrown 125 meters straight upward and then falls the same distance back to earth. Neglecting air resistance, its total time in the air is about
10 s
A 10-kg brick and a 1-kg book are dropped in a vacuum. The force of gravity on the 10-kg brick is
10 times as much as the force on the 1-kg book
A bag of groceries has a mass of 10 kilograms and a weight of about
100 N
What is the maximum resultant possible when adding a 3-N force to an 8-N force?
11 N
The mass of a sheep that weighs 110 N is about
11 kg
Suppose a small plane can fly at 200 km/h relative to the surrounding air. Suppose also that there is a 40-km/h tail wind. How fast does the plane's shadow move across the ground?
240 km/h
A girl whose weight is 500 N hangs from the middle of a bar supported by two vertical strands of rope. What is the tension in each strand?
250 N
A girl pulls on a 10-kg wagon with a constant force of 30 N. What is the wagon's acceleration?
3.0 m/s/s
A 15-N force and a 45-N force act on an object in opposite directions. What is the net force on the object?
30 N
How much does a 3.0-kg bag of bolts weigh?
30 N
A 5-N force and a 30-N force act in the same direction on an object. What is the net force on the object?
35 N
Two forces are applied on a soccer ball simultaneously. One player kicks the ball with a force of 20 N North. The other player kicks the ball with a force of 30 N West. What is the magnitude of the net force applied on the soccer ball?
36 N
A water balloon is launched at an angle of 45 degrees to the horizontal with a velocity of 20 m/s. How far away horizontally will it land? (g = -10 m/s/s)
39 m
A radar transmitter sends out a pulse that is reflected from the moon's surface. The signal returns 2.7 s after it is sent ( i.e. it goes there and back ). What is the best estimate of the moon's distance from the earth if light travels at 3.0x108 m/s?
4.0x10^8 m
A jumbo jet cruises at a constant velocity when the total thrust of the engines on the jet is 40,000 N. How much air resistance acts on the jet?
40,000 N
Two people pull on a rope in a tug-of-war. Each pulls with 400 N of force. What is the tension in the rope?
400 N
In the absence of air resistance, the angle at which a thrown ball will go the farthest is
45 degrees
Suppose a car is moving in a straight line and steadily increases its speed. It moves from 35 km/h to 40 km/h the first second and from 40 km/h to 45 km/h the next second. What is the car's acceleration?
5 km/hr x s
Suppose a jumper claims a hang time of 2 seconds. Then that jumper must be able to jump a vertical distance of
5 m
What is the resultant of a 3-unit vector and 4-unit vector at right angles to each other?
5 units.
A person is attracted towards the center of the earth by a 500-N gravitational force. The force with which the earth is attracted toward the person is
500 N
A 10-N falling object encounters 4 N of air resistance. The magnitude of the net force on the object is
6 N
A block is dragged without acceleration in a straight-line path across a level surface by a force of 6 N. What is the frictional force between the block and the surface?
6 N
A ball is hurled into the air at an angle of 30 degrees and lands on a target that is at the same level as that where the ball started. The ball will also land on the target if it is thrown at an angle of
60 degrees
Suppose you take a trip that covers 180 km and takes 3 hours to make. Your average speed is
60 km/h
A boulder rolls off an 80 meter high cliff at with a speed of 15 m/s. How far horizontally from the cliff will the boulder land? (g = -10 m/s/s)
60 m
Which best approximates the resultant of a pair of 6-unit vectors at right angles to each other?
8 units.
An apple weighs 1 N. When held at rest above your head, the net force on the apple is
9 N
Two blocks of different masses are released from rest at the top of an frictionless incline plane. How does the net force acting on each block compare? (Neglect friction)
A bigger net force is exerted on the more massive block
Which of the following would exert the most pressure on the ground?
A woman standing in high-heel shoes
Compared to its weight on earth, a 10-kg object on the moon will weigh
less
An object maintains its state of motion because it has
mass
An airplane flying into a head wind loses ground speed relative to the ground, and an airplane flying with the wind gains ground speed relative to the ground. If an airplane flies at right angles to the wind, then the speed relative to the ground is
more
If the force of gravity suddenly stopped acting on the planets, they would
move in straight lines tangent to their orbits.
always, sometimes, never; If an object is pushed or pulled and it remains at rest, there must be a force keeping it at rest that is larger than the pushing or pulling force.
never true
always, sometimes, never; No movement means no forces.
never true
In Chapter 2, you learned about "hang time," the time a jumper's feet are off the ground in a vertical jump. If the jumper runs horizontally and has the same vertical component of takeoff velocity, hang time will be
no different
Jon can jump vertically 1 meter from his skateboard when it is at rest. When the skateboard is moving horizontally, Jon can jump
no higher
Friction is a force that always acts
opposite to an object's motion.
The astronomer Copernicus publicly stated in the 1500s that Earth
revolves around the sun
When in orbit, a satellite such as the space shuttle is
simply a projectile.
always, sometimes, never; Acceleration is in the direction that the object is moving.
sometimes true
always, sometimes, never; The motion of an object is in the direction of the net force applied to the object.
sometimes true
always, sometimes, never; The product of mass and acceleration, ma, is a force.
sometimes true
The weight of a person can be represented by a vector that acts
straight down, even if the person is standing on a hill.
The reason a tennis ball and a solid steel ball will accelerate at the same rate, in the absence of air resistance, is that
the ball with the larger force also has the larger mass.
If you drop a feather and a coin at the same time in a tube filled with air, which will reach the bottom of the tube first?
the coin
A player hits a ball with a bat. The action force is the impact of the bat against the ball. What is the reaction to this force?
the force of the ball against the bat
A heavy person and a light person parachute together and wear the same size parachutes. Assuming they open their parachutes at the same time, which person reaches the ground first?
the heavy person
Strange as it may seem, it is just as hard to push a car on the moon as it is to push the same car on earth. This is because
the mass of the car is independent of gravity
A sheet of paper can be withdrawn from under a container of milk without toppling it if the paper is jerked quickly. The reason this can be done is that
the milk carton has inertia
You would have the largest mass of gold if your chunk of gold weighed 1 N on
the moon
An object weighs 30 N on earth. A second object weighs 30 N on the moon. Which has the greater mass?
the one on the moon
As a ball falls, the action force is the pull of the earth's mass on the ball. What is the reaction to this force?
the pull of the ball's mass on the earth
An archer shoots an arrow. Consider the action force to be the bowstring against the arrow. The reaction to this force is the
arrow's push against the bowstring
At what part of a path does a projectile have minimum speed?
at the top of its path
The law of inertia applies to
both moving and non-moving objects.
Suppose a particle is accelerated through space by a constant 10-N force. Suddenly the particle encounters a second force of 10-N in a direction opposite to that of the first force. The particle
continues at the speed it had when it encountered the second force.
Aunt Minnie throws a rock downward, and air resistance is negligible. Compared to a rock that is dropped, the acceleration of the rock after it is thrown is
the same
Compared to its mass on Earth, the mass of a 10-kg object on the moon is
the same
A cannonball is launched from the ground at an angle of 30 degrees and a speed of 20 m/s. Ideally (no air resistance) the ball will land on the ground with a speed of
-20 m/s
Mr. Vining is looking at new Garden apartment in downtown Scottsdale and is out on the balcony and decides to find out how far up he is. He takes out a water balloon (he now always carries a few thanks to Mr. Hill) and drops it over the railing. If it takes 3.0 s to hit the ground, how far is the ground beneath him? (g=-10m/s2)
-45 m
An object is released from a height of 11 m. Which one of the following best represents the displacement of the object 1.0 s after it falls freely from rest? (g = -10 m/s2)
-5.0 m
An object is dropped and falls freely to the ground with an acceleration of -9.8 m/s/s. If it is thrown upward at an angle instead, its acceleration after it is thrown would be
-9.8 m/s/s
The acceleration due to gravity on earth is approximately
-10 m/s^2
A body falls freely from rest near the surface of the earth. The distance the object falls in 2 seconds is
-20 m
A ball is thrown straight upward at 20 m/s. Ideally (no air resistance) the ball will return to the thrower's hand with a velocity of
-20 m/s
The average velocity of an object is 2 meters per second for 6.0 seconds. What is the total distance traveled by the object?
12 m
A runner travels 60.0 m at a steady speed of 5.0 m/s. The time taken is
12 s
Which of the following is NOT a vector quantity?
5 m/s
Starting from rest, an object rolls freely down an incline that is 10 meters long in 2 seconds. The acceleration of the object is approximately
5 m/s^2
Starting from rest, the distance a freely falling object will fall in 10 seconds is about
500 m
If a car increases its velocity from zero to 60 km/h in 10 seconds, it acceleration is
6 km/h/s
A car accelerates from rest at 2 meters per second per second. What is its speed 3 seconds after the car starts moving?
6 m/s
a car starts from rest and after 7 seconds, it is moving at 42 m/s. what is the car's avg acceleration?
6 m/s^2
If a projectile is fired straight up at a speed of 30 m/s, the total time to return to its starting point is about
6 seconds
Mr. Hill is very upset with Mr. Vining and he picks Mr. Vining up and throws him into the air. What can be said about Mr. Vining's acceleration after Mr. Hill releases him and before he hits the ground?
Mr. Vining's acceleration is always about -10 m/s2
Which one of the following statements correctly describes the motion of an object depicted by the position vs. time graph below?
The object has constant velocity
A ball thrown in the air will never go as far as physics ideally would predict because
air friction slows the ball
In the absence of air friction, the horizontal component of a projectile's velocity doesn't change as the projectile moves. always, sometimes, never.
always true
If a body has an acceleration of -3 m/s2, it MUST be slowing down. true or false?
false
While driving a car, it is possible to make a turn without accelerating if you keep the speed constant while turning. true or false?
false
a ball is thrown into the air. at the highest point, the ball has zero velocity and zero acceleration. t or f.
false
true or false; A quantity that has both magnitude and direction is called a scalar.
false
true or false; A quantity that has only magnitude is called a vector.
false
Consider drops of water leaking from a water faucet. (Ignore air resistance.) As the drops fall they remain at a relatively fixed distance from each other.
get farther apart
When you look at the speedometer in a moving car, you can see the car's
instantaneous speed
The hang time (time one's feet are off the ground in a jump) for most athletes is
less than 1 second
A ball is thrown upwards and caught when it comes back down. In the presence of air resistance, the speed with which it is caught is
less than the speed it had when thrown upwards
A scalar is a quantity that has
magnitude
A vector is a quantity that has
magnitude and direction
A bullet is dropped from the top of the Empire State Building while another bullet is fired downward and is out of the gun from the same location. Neglecting air resistance, acceleration is greatest for the
neither it's -10 m/s2 for each and both are in motion
Drop a rock from a 5 m height and it accelerates at -10 m/s/s and strikes the ground 1 s later. Drop the same rock from a height of 2.5 m and its acceleration of the fall is
the same
a ball is thrown upwards and caught when it comes back down. in the absence of air resistance, the speed of the ball the instant before it is caught would be
the same as the speed it had when thrown upwards
one possible unit of speed is
-miles per hour -light years per century - kilometers per hour
An object travels 8 meters in the first second of travel, 8 meters again during the second second of travel, and 8 meters again during the third second. Its acceleration in meters per second per second is
0
What is the acceleration of a car that maintains a constant velocity of 100 km/h for 10 seconds?
0
a car accelerates at 2 m/s/s. assuming the car starts from rest, how much time does it need to accelerate to a speed of 20 m/s?
10 seconds
A rifle with a muzzle velocity of 100 m/s is fired horizontally from a tower. Neglecting air resistance, where will the bullet be 1 second later?
100 m downrange
true or false; All motion, including constant-velocity motion, are sustained by a "force of motion".
false
true or false; An object in motion stays in motion because of the inertia force acting on it.
false
true or false; Excluding the force due to air pressure, there is only one force acting on a book lying at rest on a table top.
false
true or false; If an object is pushed or pulled and it remains at rest because of its inertia (its mass is too great).
false
true or false; If velocity is zero, then acceleration must be zero too.
false
true or false; If you slide a hockey puck across a frictionless ice rink, there must be a horizontal force on it to keep it in motion.
false
true or false; In order to make a cart move forward, a horse must pull harder on the cart than the cart pulls on the horse.
false
true or false; Inertia is just another way of saying weight.
false
true or false; It is possible for an object in free fall to have zero acceleration.
false
true or false; Mass is a vector quantity.
false
true or false; Only living things can exert forces on other things.
false
true or false; Speed is proportional to force (Ex. The higher the speed, the higher the force)
false
true or false; The SI unit of mass is the newton.
false
true or false; The acceleration of an object is inversely proportional to the net force acting on it.
false
true or false; The amount of matter in an object is called its weight.
false
true or false; The higher the velocity, the higher the acceleration.
false
true or false; The reason a car moves at constant speed along the road is because the friction between the tires and the road causes a forward reaction force to act on the car.
false
true or false; The speed of an object dropped in air will continue to increase without limit.
false
true or false; There is no connection between Newton's Laws and kinematics (motion equations).
false
true or false; Velocity is a force.
false
Accelerations are produced by
forces
An object following a straight-line path at constant speed
has zero acceleration
Mass is a measure of an object's
inertia
One object has twice as much mass as another object. The first object also has twice as much
inertia
How does acceleration of an object change in relation to its mass? It is
inversely proportional.
When a basketball player jumps to make a shot, once the feet are off the floor, the jumper's acceleration
is -9.8 m/s/s; no more, no less
A projectile is fired horizontally in a vacuum. The projectile maintains its horizontal component of speed because it
is not acted on by any horizontal forces.
If you could throw a baseball horizontally at a speed of 8 km/s and if there were no air drag and nothing to stop it,
it would orbit Earth.
A rock is thrown vertically into the air. At the very top of its trajectory the net force on it is
its weight
Which of the following is NOT an acceleration unit?
km/s
speed is
-a measure of how fast something is moving -the distance covered per unit time -always measured in terms of a unit of distance divided by a unit of time
Friction
- acts in a direction that opposes the motion of an object - comes from microscopic bumps that act as obstructions to the object's motion - is the name given to the force acting between surfaces sliding past one another
Equilibrium occurs when
- all the forces acting on an object are balanced. - the sum of the +x forces on an object equals the sum of the -x forces. - the net force on the object is zero. - the sum of the upward forces equals the sum of the downward forces.
In order to find the components of a vector, you should
- draw the vector with correct magnitude and orientation. - measure the sides of the rectangle. - draw a rectangle so that the vector is the diagonal
The acceleration produced by a net force on an object is
- inversely proportional to the mass of the object. - directly proportional to the magnitude of the net force. - in the same direction as the net force.
The law of inertia states that an object
- will continue moving at the same velocity unless an outside force acts on it. - will continue moving in a straight line unless an outside force acts on it. - that is not moving will never move unless a force acts on it. - at rest will remain at rest unless acted on by an outside force.
In the absence of air resistance, at what other angle will a thrown ball go the same distance as one thrown at an angle of 75 degrees?
15 degrees
The terminal speed for a person parachuting (with the chute open) is about
15 km/hr
A tow-truck exerts a force of 3000 N on a car, accelerating it at 2 m/s/s. What is the mass of the car?
1500 kg
A 747 jumbo jet has a mass of 30,000 kg. The thrust for each of four engines is 15,000 N. What is the jet's acceleration when taking off?
2 m/s/s
A car has a mass of 1000 kg and accelerates at 2 meters per second squared. What is the magnitude of the force acting on the car?
2000 N
Two blocks of different masses are released from rest at the top of an frictionless incline plane. How will their acceleration of each block compare? (Neglect friction)
Both balls will have the same acceleration
Which has more mass, a kilogram of feathers or a kilogram of iron?
Neither—they both have the same mass.
Galileo found that a ball rolling down one inclined plane would roll how far up another inclined plane?
To nearly its original height
A Mack truck and a Volkswagen traveling at the same speed have a head-on collision. The vehicle to undergo the greater change in velocity will be the
Volkswagen
If a freely falling object were somehow equipped with a speedometer, its speed reading would increase each second by
about 10 m/s
When something falls to the ground, it accelerates. This acceleration is called the acceleration due to gravity and is symbolized by the letter g. What is the value of g on Earth's surface?
about 10 m/s/s
An object has a constant mass. A constant net force on the object can produce constant
acceleration
A ball tossed vertically upward rises, reaches its highest point, and then falls back to its starting point. During this time the acceleration of the ball is always
directed downward
The area under a velocity-time graph represents
displacement
The two measurements necessary for calculating average speed are
distance and time
A ball is thrown into the air at some angle. At the very top of the ball's path, its velocity is
entirely horizontal
A 5000 kg car smashes into a 10,000 kg truck. The car exerts a force on the truck that is
equal to the force that the truck exerts on the car
Average speed is defined as the time it takes for a trip divided by the distance. t or f
false
a unit of acceleration is meters per second. t or f.
false
true or false; A ball will go the farthest if thrown almost horizontally.
false
true or false; A bicycle and a parked car have a head-on collision. The force of impact is greater on the bicycle.
false
true or false; A force applied by, say a hand, still acts on an object after the object leaves the hand.
false
true or false; A steel ball and a wood ball of the same size are released together from the top of a tower. In the absence of air resistance they both would reach the ground at the same time. The reason for this is that the force on each ball is the same.
false
true or false; All forces are mediated through contact; forces cannot be exerted between two things if they are not in contact.
false
A force of 3 N accelerates a mass of 3 kg at the rate of 1 m/s2. The acceleration of a mass of 6 kg acted upon by a force of 6 N is
the same.
A tennis ball and a solid steel ball with the same diameter are dropped at the same time. Which ball has the greater force acting on it?
the steel ball
The horizontal component of a projectile's velocity is independent of
the vertical component of its velocity.
A tennis ball and a solid steel ball with the same diameter are dropped at the same time. In the absence of air resistance, which ball has the greater acceleration?
they both have the same acceleration.
true or false; A single vector can be replaced by two vectors in the X and Y directions that are at right angles to one another. These two X and Y vectors are called the components of the original vector.
true
true or false; Air resistance refers to friction between the air and an object moving through the air.
true
true or false; An astronaut has the same mass on earth as in space.
true
true or false; Any vector can be represented by two vectors that are at right angles to each other.
true
true or false; Friction refers to the force between two surfaces that are sliding past one another.
true
true or false; The combination of all the forces that act on an object is called the net force.
true
true or false; The length of a vector represents its magnitude.
true
true or false; The vector sum of all the forces (or the net force) acting on an object is called the resultant.
true
true or false; Whenever one object exerts a force on another object, the second object always exerts a force back on the first object.
true
As an object freely falls, its
velocity increases
A push on a 1-kilogram brick accelerates the brick. Neglecting friction, to equally accelerate a 10 kilogram brick, one would have to push
with 10 times as much force.
The force required to maintain an object at a constant speed in free space is equal to
zero
If you were in a space ship and fired a cannon ball into frictionless space, the amount of force needed to keep it going would be
zero, since no force is necessary to keep it moving
a ball is thrown straight up. at the top of its path its instantaneous speed is
0 m/s
If a car is traveling at a constant average speed of 60 kilometers per hour, how long does it take to travel 12 kilometers?
0.2 hours
Using the Pythagorean theorem, the resultant of a 6-N force in the Y-direction and a 8-N force in the X-direction is
10 N
A cannonball is fired at some angle into the air. In the first second it moves 10 meters horizontally. Assuming it doesn't hit the ground and there is no air resistance, how far does it move horizontally in the next second?
10 m
An apple falls from a tree and hits the ground 5 m below. It hits the ground with a speed of about
10 m/s
a free falling objects starts from rest. after falling for 1 second, it will have a speed of about
10 m/s
A car accelerates at 2 m/s2. Assuming the car starts from rest, how much time does it need to accelerate to a speed of 30 m/s?
15 s
If a projectile is fired straight up at a speed of 10 m/s, the time it takes to reach the top of its path is about
1s
A car accelerates uniformly from 3.0 m/s to 12.0 m/s in 4.5 s. The magnitude of the acceleration is
2.0 m/s^2
Mr. Vining sees Mr. Hill under his balcony. Mr. Vining drops a water balloon that falls freely for 2 seconds before striking Mr. Hill on the head and getting him soaking wet. How far did the balloon travel before striking Mr. Hill?
20 m
If a freely falling object were somehow equipped with a speedometer on a planet where the acceleration due to gravity is 20 m/s/s, then its speed reading would increase each second by
20 m/s
a freely falling object starts from rest. after falling for 6 seconds, it will have a speed of about
60 m/s
Consider the following graph. The average speed is greatest during which time interval
8s - 10s
Which of the following would NOT be considered a projectile?
a cannonball rolling down a slope
Suppose an object is in free fall. Each second the object falls
a larger distance than in the second before
a ball is thrown straight up. at the top of its path, its acc is
about 10 m/s/s
It takes 6 s for a stone to fall to the bottom of a mineshaft. How deep is the shaft?
about 180 m
The position vs. time graph below represents the relationship between distance and time for an object moving in a straight line. According to the graph, the object is
accelerating
In the absence of air resistance, objects fall at constant
acceleration
If an object falls with constant acceleration, the velocity of the object must
continually change by the same amount each second
If you drop a feather and a coin at the same time in a vacuum tube, which will reach the bottom of the tube first?
neither, they will reach the bottom at the same time.
At the instant a ball is thrown horizontally with a large force, an identical ball is dropped from the same height. Which ball hits the ground first?
neither-they both hit the ground at the same time
In the absence of air friction, the vertical component of a projectile's velocity doesn't change as the projectile moves. always, sometimes, never.
never true
Galileo's use of inclined planes allowed him to effectively
slow down the acceleration of free fall
Change in velocity can be obtained from
the area under an acceleration-time graph
After a rock that is thrown straight up reaches the top of its path and is starting to fall back down, its acceleration is (neglect air resistance)
the same as when it was at the top of its path
A ball is thrown upwards and caught when it comes back down. Neglecting air resistance, its speed when caught is
the same speed it had when thrown upwards
A bullet fired horizontally hits the ground in 0.5 seconds. If it had been fired with a much higher speed in the same direction, it would have hit the ground (neglecting the Earth's curvature and air resistance) in
the same time - 0.5 s
Two balls that are exactly the same size and shape. One ball is made out of aluminum and has a mass of a 0.5 kg. The other one is made out of uranium (its covered with lead so that no radiation leaks out) and has a mass of a 6.0 kg. If they are released at the same instant from the same height of 20 m they will reach the ground at
the same time with the same speeds
An object thrown straight up has a positive velocity and a negative acceleration. true or false?
true
If a body travels at constant speed, then the distance it travels varies directly with the time elapsed. true or false?
true
even though a car is slowing down, it is still accelerating, in the most general definition of acceleration. t or f.
true
On a position vs. time graph, the slope of the line represents the
velocity
Acceleration is defined as the CHANGE in
velocity divided by the time interval
As an object falls freely in a vacuum(no air resistance), its
velocity increases
When a rock thrown straight upwards gets to the exact top of its path, its
velocity is zero, and its acceleration is about -10 m/s^2
Suppose you are in a car that is going around a curve. The speedometer reads a constant 30 miles per hour. Which of the following is NOT true?
your velocity is constant