physics mid-term exam
carl lewis set a world record for the 100.0m run with a time of 9.86s. if after reaching the finish line he walked directly back to his starting point in 90.9s, what is the magnitude of his average velocity for the 200.0m? A) 0 m/s B) 1.10 m/s C) 1.98 m/s D) 5.60 m/s E) 10.1 m/s
A) 0 m/s
a ball is thrown vertically upward from the surface of the earth. consider the following quantities: 1) speed of the ball 2) velocity of the ball 3) acceleration of the ball which of these is (are) zero when the ball has reached its maximum height? A) 1 and 2 B) 1 and 3 C) 1 D) 2 E) 1, 2, and 3
A) 1 and 2
when a projectile is shot up at a 45 degree angle from the ground the speed in the horizontal direction will (1) and the speed in the vertical direction will (2) on the way up and then (3) on the way down A) 1- constant 2- decrease 3- increase B) 1- increase 2- decrease 3- increase C) 1-decrease 2- increase 3- decrease D) 1- constant 2- increase 3- decrease
A) 1- constant 2- decrease 3- increase
if a rock on a cliff has a mass of 15 kg and is 50 m off the ground, then how much will the kinetic energy be when the rock is 25 m off the ground? A) 1/2 the potential B) 1/4 the potential C) 4 times the potential D) 2 times the potential
A) 1/2 the potential
a 1 kg apple falls from rest, 5 m to the ground. the apple hits the ground with an impact speed of about A) 10 m/s B) 20 m/s C) 40 m/s D) 7.07 m/s E) not enough information to say
A) 10 m/s
[velocity vs time graph with positive linear slope. points (0 s , 5 m/s ) and (5 s , 25 m/s)] determine the acceleration of the object as portrayed by the graph A) 4 m/s^2 B) 5 m/s^2 C) 4 m/s D 5 m/s
A) 4 m/s^2
a person is attracted towards the center of the earth by a 440 N gravitational force. the force with which the earth is attracted toward the person is A) 440 N B) very very small C) very very large
A) 440 N
which of the following is an accurate statement> A) a vector cannot have zero magnitude if one of its components is not zero B) the magnitude of a vector can be less than the magnitude of one of its components C) if the magnitude of vector A is less than the magnitude of vector B, then the x-component of A is less than the x-component of B D) the magnitude of a vector can be positive or negative
A) a vector cannot have zero magnitude if one of its components is not zero
in all machines energy is lost in one form or another. therefore there is not perpetual motion machine. the only way to keep a machine going is to A) do work on the system B) add more friction to it C) do nothing to it D) add more inertia to it
A) do work on the system
what force causes things to slow down and lose their energy as heat? A) friction B) tension C) gravitational D) electrical
A) friction
a block is at rest on an incline. the force of friction necessary to prevent the block from sliding increases when the incline angle is A) increased B) decreased C) neither A nor B (force of friction stays the same)
A) increased
An unfortunate bug splatters against the windshield of a moving car. Compared to the deceleration of the car, the deceleration of the bug is A) larger B) the same C) smaller
A) larger
An airplane flying into a head wind loses ground speed, and an airplane flying with the wind gains ground speed. If an airplane flies at right angles to the wind, then ground speed is A) more B) unchanged C) less
A) more
why is it more important to have seat belts in a car than a bus? A) the larger mass of the bus will cause a smaller change in velocity and so the kids inertia won't cause them to fly out the window B) the larger mass of the mus will cause them to have a larger change in velocity and so the kids inertia won't cause them to fly out the window C) because bus drivers don't drive crazy
A) the larger mass of the bus will cause a smaller change in velocity and so the kids inertia won't cause them to fly out the window
a space vehicle of mass m has a speed v. at some instant, it separates into two pieces, each of mass .5m. one of the pieces is at rest just after the separation. which one of the following statements is true? A) the moving piece has speed 2v B) this process conserves kinetic energy C) the piece at rest possesses kinetic energy D) this process does not conserve total energy E) this process does not conserve momentum
A) the moving piece has a speed 2v
you are standing in a moving bus, facing forward, and you suddenly fall forward. you can imply from this that the bus's A) velocity decreased B) velocity increased C) speed remained the same but it's turning to the right D) speed remained the same but it's turning to the left
A) velocity decreased
a women can lift barrels a vertical distance of 1 meter or can roll them up a 2 m long ramp to the same elevation. if she uses the ramp to do the same amount of work, how much force is applied to the barrel to move it to the same height? A) 1/4 as much B) 1/2 as much C) the same amount D) 2 times as much E) 4 times as much
B) 1/2 as much
which of the following is a vector expression? A) 10 N B) 10 N east C) 7.0 kg D) 7 s
B) 10 N east
A piece of putty moving with 2 units of momentum strikes and sticks to a heavy bowling ball that is initially at rest. After the putty sticks to the ball, both are set in motion with a combined momentum that is A) less than 2 units B) 2 units C) more than 2 units D) not enough information to say
B) 2 units
You pull horizontally on a 50 kg crate with a force of 450 N and the friction force on the crate is 250 N. The acceleration of the crate is A) 2 B) 4 C) 9 D) 14
B) 4
two objects A and B accelerate from rest with the same constant acceleration. A accelerates for twice as much as B. which of the following statements is true concerning these objects at the end of their respective periods of acceleration? A) A will travel twice as far as B B) A will travel four times as far as B C) A will travel eight times further than B D) A will be moving four times faster than B E) A will be moving eight times faster than B
B) A will travel four times as far as B
a 10 N force is applied to push a block across a friction free surface for a displacement of 5 m to the right. determine which force(s) have work done on them A) F normal B) F applied C) F gravitational
B) F applied
the horizontal component of a projectile's velocity is A) effected by the acceleration of gravity B) a constant value throughout the trip C) zero throughout the motion of the object
B) a constant value throughout the trip
in which one of the following systems is there a decrease in gravitational potential energy? A) a boy stretches a horizontal spring B) a girl jumps down from a bed C) a crate rests at the bottom of an inclined plane D) a car ascends a steep hill E) water is forced upward through a pipe
B) a girl jumps down from a bed
which as more kinetic energy? A) an elephant sleeping B) a small but not so normal mouse flying through the air at 100 m/s C) a normal cat running behind the mouse at 10 m/s
B) a small but not so normal mouse flying through the air at 100 m/s
A cannon recoils from launching a cannonball. The speed of the cannon's recoil is small because the A) impulse on the cannon is less than the impulse on the cannonball B) cannon has far more mass than the cannonball C) the momentum of the cannon is unchanged D) force against the cannon is relatively small
B) cannon has far more mass than the cannonball
Two displacement vectors have magnitudes of 5.0 m and 7.0 m, respectively. When these two vectors are added, the magnitude of the sum A) is 2.0 m B) could be any value between 2 and 12 m C) is 12 m D) is larger than 12 m
B) could be any value between 2 and 12 m
what is the direction of the acceleration of the mass of a object with a net force of 2 N left? A) right B) left C) not accelerating D) up
B) left
two objects constitute an isolated system. in an elastic collision between the two objects, which one of the following statements is a false statement? A) the total kinetic energy is conserved B) the kinetic energy of each object is the same before and after the collision C) the total momentum is conserved D) the magnitude of the force exerted by each object on the other object is equal E) the total kinetic energy before the collision is equal to the total kinetic energy after the collision
B) the kinetic energy of each object is the same before and after the collision
two balls of equal size are dropped from the same height from the roof of a building. one ball has twice the mass of the other. when the balls reach the ground, how do the kinetic energies of the two balls compare? A) the lighter one has 1/4 as much KE B) the lighter one has 1/2 as much KE C) the lighter one has the same KE D) the lighter one has twice as much KE E) the lighter one has four times as much KE
B) the lighter one has 1/2 as much KE
a rock is thrown vertically upwards from the surface of the earth. the rock rises to some maximum height and falls back down towards the surface of the earth. which one of the following statements concerning this situation is true if air resistance is neglected? A) as the rock rises, its acceleration vector points upward B) the rock is a freely falling body for the duration of its flight C) the acceleration of the rock is zero when the rock is at its highest point D) the speed of the rock is negative while the ball falls back to the earth E) the velocity and acceleration are always in the same direction
B) the rock is a free falling body for the duration of its flight
A stone is thrown horizontally from the top of a tower at the same instant a ball is dropped vertically. Which object is traveling faster when it hits the level ground below? A) it is impossible to tell from the information given B) the stone C) the ball D) neither, since both are traveling at the same speed
B) the stone
a roller coaster starts from rest at the top of an 18 m hill. the car travels to the bottom of the hill and continues up the next hill that is 10 m high. how fast is the car moving at the top of the 10 m hill if friction is ignored? A) 6.4 m/s B) 8.1 m/s C) 13 m/s D) 18 m/s E) 27 m/s
C) 13 m/s
a woman stands on the edge of a cliff and throws a stone vertically downward with an initial speed of 10 m/s. the instant before the stone hits the ground below, it has 450 J of kinetic energy. if she were to throw the stone horizontally outward from the cliff with the same initial speed, how much kinetic energy would it have just before it hits the ground? A) 0 J B) < 450 J C) 450 J D) > 450 J
C) 450 J
if you push with 6 N on an object to the right along a surface of a table and it moves at a constant velocity of 2 m/s, determine the magnitude friction force on the object A) 0 N B) 12 N C) 6 N D) 3 N
C) 6 N
a spring-loaded gun is aimed horizontally and is used to launch identical balls with different initial speeds. the gun is at a fixed position above the floor. the balls are fired one at a time. if the speed of the second ball fired is twice the speed of the first ball fired, how is the horizontal range affected? A) the range for both balls will be the same B) R of second ball with be half as much as R of the first C) R of second ball will be twice as large as R of the first D) R of the second ball will be about 1.4 times larger than that of the first E) R of the second ball will be smaller than R of the first by 1.4
C) R of the second ball will be twice as large as R of the first
which of the following would be considered a projectile? A) a cannonball thrown straight up B) a cannonball rolling down a level street C) a cannonball rolling off the edge of a table D) a cannonball dropped from the side of a cliff E) all of the above are projectiles
C) a cannonball rolling off the edge of a table
a new car manufacturer advertises that their car can go "from zero to sixty in 8 seconds". this is a description of: A) average speed B) instantaneous speed C) average acceleration D) instantaneous acceleration
C) average acceleration
two balls are thrown horizontally with different speeds from the same height. which one is in the air longer? A) the faster object B) the slower object C) both have the same air time
C) both have the same air time
when the angle of an incline with a block resting on it increases, the normal support force A) increases B) stays the same C) decreases
C) decreases
which of the following is a vector quantity? A) time B) average speed C) displacement D) length E) distance
C) displacement
the acceleration of an Atwood machine is always A) 0 B) negative C) fraction of acceleration of gravity D) greater than the acceleration of gravity
C) fraction of acceleration of gravity
a bicyclist is riding at a constant speed along a straight path. the rider throws a ball straight up to a height a few meters above her head. ignoring air resistance, where will the ball land? A) behind the rider B) in front of the rider C) in the same hand that threw the ball D) in the opposite had to the one that threw it E) this cannot be determined without knowing the speed of the rider and the maximum height of the ball
C) in the same hand that threw the ball
if bronco billy the skydiver if falling he is losing potential energy as he gets closer to the ground, but after a while he stops accelerating. so what is happening to the energy? A) it is destroyed B) it is transformed into greater kinetic energy C) it is transformed into greater thermal energy
C) it is transformed into greater thermal energy
a ball is thrown into the air with 100 J of kinetic energy, which is transformed to gravitational potential energy at the top of its trajectory. when it returns to its original level after encountering air resistance, its kinetic energy is A) 100 J B) more than 100 J C) less than 100 J D) not enough information given
C) less than 100 J
two cars collide head on. at every moment during the collision, the magnitude of the force the first car exerts on the second is exactly equal to the magnitude of the force the second car exerts on the first. this is an example of A) newton's first law B) newton's second law C) newton's third law D) newton's law of gravitation
C) newton's third law
which of the following quantities is a vector? A) the age of the earth B) the mass of a freight train C) the earth's pull on your body D) the temperature of a hot cup of coffee E) the number of people attending a soccer game
C) the earth's pull on your body
a rock is suspended from a string and is moving downward at a constant velocity. which statement is true concerning the tension in the string if air resistance is ignored? A) the tension is 0 N B) the tension points downwards C) the tension is equal to the weight of the rock D) the tension is less than the weight of the rock E) the tension is greater than the weight of the rock
C) the tension is equal to the weight of the rock
A bullet is fired horizontally, and at the same instant a second bullet is dropped from the same height. Ignore air resistance. Compare the times of fall of the two bullets. A) the fired bullet hits first B) the dropped bullet hits first C) they hit at the same time D) cannot tell without knowing the masses
C) they hit at the same time
A red marble moving to the right at .4 m/s has a head on, elastic collision with a blue marble of the same mass sitting at rest on a smooth, level surface. Which of the following are the correct magnitudes and directions of the velocities of the two marbles after the collision? Red Blue A) .35 m/s left .25 m/s right B) .4 m/s right .3 m/s right C) zero m/s .4 m/s right D) .2 m/s left .2 m/s right E) .4 m/s left zero m/s
C) zero m/s .4 m/s right
if an object is pushed with 5 N of force to the right and also pushed with 7 N of force to the left, what is the net force on the object? A) 12 N right B) 2 N right C) 12 N left D) 2 N left
D) 2 N left
An Olympic athlete throws a javelin at four different angles above the horizontal, each with the same speed: 30°, 40°, 60°, and 80°. Which two throws cause the javelin to land the same distance away? A) 30 and 80 B) 40 and 60 C) 40 and 80 D) 30 and 60
D) 30 and 60
a motorcycle has a velocity of 15 m/s due north as it passes a car with a velocity of 24 m/s due south. what is the magnitude and direction of the velocity of the motorcycle as seen by the driver of the car? A) 9 m/s north B) 9 m/s south C) 15 m/s north D) 39 m/s north E) 39 m/s south
D) 39 m/s north
how much force is needed to accelerate a 4 kg physics book to an acceleration of 2 m/s^2? A) 0 N B) 2 N C) .5 N D) 8 N E) 24 N
D) 8 N
in which situation is zero net work done? A) a ball rolls down an inclined plane B) a physics student stretches a spring C) a projectile falls toward the surface of the earth D) a box is pulled across a rough floor at constant velocity E) a child pulls a wagon across a rough surface causing it to accelerate
D) a box is pulled across a rough floor at constant velocity
ball A is dropped from rest from a window. at the same instant ball B is thrown downward and ball C is thrown upward from the same window. which statement is concerning the balls after their release is necessarily true if air resistance is neglected? A) at some instant after it is thrown, the acceleration of ball C is zero B) all three balls strike the ground at the same time C) all three balls have the same velocity at any instant D) all three balls have the same acceleration at any instant E) all three balls reach the ground with the same velocity
D) all three balls have the same acceleration at any instant
a stone is thrown straight up. at the top of its path, the net force acting on it is A) greater than its weight B) greater than zero but less than its weight C) instantaneously equal to zero D) equal to its weight
D) equal to its weight
you are trying to cross a river that flows due south with a strong current. you start out in your motorboat on the east bank desiring to reach the west bank directly west from your starting point. you should head your motorboat A) due west B) due north C) in a southwesterly direction D) in a northwesterly direction
D) in a northwesterly direction
when you look at the speedometer in a moving car, you can see the car's A) average distance traveled B) instantaneous acceleration C) average speed D) instantaneous speed E) average acceleration
D) instantaneous speed
in the absence of an external force, a moving object will A) stop immediately B) slow down and eventually come to a stop C) go faster and faster D) move with constant velocity
D) move with constant velocity
(velocity vs time graph with a negative linear slope) the object whose motion is represented by this graph is A) moving in a negative direction B) moving with a constant velocity C) moving with a negative velocity D) moving with a constant negative acceleration E) moving with a constant positive acceleration
D) moving with a constant negative acceleration
in which of the following situations does the car have an eastward acceleration? A) the car travels westward at a constant speed B) the car travels westward and speeds up C) the car travels eastward and slows down D) the car travels westward and slows down E) the car starts from rest and moves towards the west
D) the car travels westward and slows down
a rock is thrown straight up from the surface of the earth. which one of the following statements describes the energy transformation of the rock as it rises? neglect air resistance A) the total energy of the rock increases B) the kinetic energy increases and the potential energy decreases C) both potential and total increase D) the kinetic energy decreases and the potential energy increases E) both remain
D) the kinetic energy decreases and the potential energy increases
starting from rest, a particle that is confined to move along a straight line is accelerated at a rate of 5.0 m/s^2. which statement concerning the slope of the position versus time graph for this particle is true? A) the slope has a constant value of 5.0 m/s B) the slope has a constant value of 5.0 m/s^2 C) the slope is both constant and negative D) the slope is not constant and increases with increasing time E) the slope is not constant and decreases with increasing time
D) the slope is not constant and increases with increasing time
Stationary fireworks explodes in space breaking into a number of small fragments. At the location of the explosion, the net force due to gravity is zero newtons. Which one of the following statements concerning the event is true? A) kinetic energy is conserved in the process B) the fragments must have equal kinetic energies C) the sum of the kinetic energies of the fragments must be zero D) the vector sum of the linear momenta of the fragments must be zero E) the velocity of any one fragment must be equal to the velocity of any other fragment
D) the vector sum of the linear momenta of the fragments must be zero
a baseball is hit upward and travels along a parabolic arc before it strikes the ground. which one of the following statements is necessarily true? A) the acceleration of the ball decreases as the ball moves upward B) the velocity of the ball is zero when the ball is at the highest point of the arc C) the acceleration of the ball is zero when the ball is at the highest point in the arc D) the x-component of the velocity of the ball is the same throughout the ball's flight E) the velocity of the ball is a maximum when the ball is at the highest point in the arc
D) the x-component of the velocity of the ball is the same throughout the ball's flight
If you lift one load up two stories, how much work do you do compared to lifting one load up only one story? A) one quarter as much B) one half as much C) the same amount D) twice as much E) four times as much
D) twice as much
a constant force of 25 N is applied as shown to a block which undergoes a displacement of 7.5 m to the right along a frictionless surface while the force acts. what is the work done by the force? A) zero joules B) +94 J C) -94 J D) +160 J E) -160 J
E) -160 J
estimate the amount of power needed to lift a 10 kg box 2 m in 1 second A) 50 W B) 5 W C) 20 W D) 230 W E) 200 W
E) 200 W
a police car is in pursuit of a stolen pickup truck, at one instant, the car has a speed of 35 m/s and is 250 m behind the truck, at the same time, the truck has a speed of 30 m/s. if neither vehicle accelerates, how long will it take the police to catch up to the truck? A) 5 s B) 65 s C) 30 s D) 82 s E) 50 s
E) 50 s
what is the estimate of the weight of a kid that has a mass of 66.0 kg? A) 660 N up B) 660 kg down C) 66.0 N down D) 66.0 kg up E) 660 N down
E) 660 N down
As a pendulum swings back and forth A) at the end points of its swing, its energy is all potential B) at the lowest part of its swing, its energy is all kinetic C) kinetic energy is transformed into potential energy D) potential energy is transformed into kinetic energy E) all of the above
E) all of the above
in physics, work is defined as A) force times time B) force divided by distance C) distance divided by time D) force divided by time E) force times distance
E) force times distance
A stunt person jumps from the roof of a tall building, but no injury occurs because the person lands on a large, air-filled bag. Which one of the following best describes why no injury occurs? A) the bag provides the necessary force to stop the person B) the bag reduces the impulse to the person C) the bag increases the time the force acts on the person and reduces the change in momentum D) the bag decreases the amount of time during which the momentum is changing and reduces the average force on the person E) the bag increases the amount of time during which the momentum is changing and reduces the average force on the person
E) the bag increases the amount of time during which the momentum is changing and reduces the average force on the person
an elevator supported by a single cable descends a shaft at a constant speed. the only forces acting on the elevator are the tension in the cable and the gravitational force. which one of the following statements is true? A) the magnitude of the work done by the tension force is larger than that done by the gravitational force B) the magnitude of the work done by the gravitational force in larger than that done by the tension force C) the work done by the tension force is zero joules D) the work done by the gravitational force is zero joules E) the net work done by the two forces is zero joules
E) the net work done by the two forces is zero joules
a tennis ball is thrown upward at an angle from point A. it follows a parabolic trajectory and hits the ground at point D. point C marks its highest position of the ball. point B is half way between A and C. while in flight how do the x and y components of the velocity vector of the ball compare at the point A and D? A) the velocity components are non-zero at A and are zero at D B) the velocity components are the same in magnitude and direction at both points C) the velocity components have the same magnitudes at both points but their directions are reversed D) the velocity components have the same magnitudes at both points but the directions of the x-components are reversed E) the velocity components have the same magnitude at both points but the directions of the y-components are reversed
E) the velocity components have the same magnitude at both point but the directions of the y-components are reversed