Question 1

A driver,traveling at 22 m/s,slows down her 2000 kg truck to stop for a red light.What work is done on the truck by the friction force exerted by the road on the truck?

Accepted Answer

A) -2.2 × 104 J 
B) -4.4 × 104 J 
C) -4.8 × 105 J 
D) -9.7 × 105 J

Question 2

A 500-kg elevator is pulled upward by a cable that exerts a constant force of 5500 N on the elevator for a distance of 50.0 m.The elevator is the system.
(a)What is the work done by the 5500-N force?
(b)What is the work done by the gravitational force?
(c)What is the net work done on the elevator?

Accepted Answer

The answer of A 500-kg elevator is pulled upward by...

Question 3

On a horizontal frictionless air table,a puck runs into an ideal horizontal spring that is fastened to the table.The puck compresses the spring by 15 cm before coming to rest.During the compression process,which quantities are conserved?

Accepted Answer

A) only the momentum of the puck 
B) only the kinetic energy of the puck 
C) only the mechanical energy (kinetic plus potential)of the puck 
D) the momentum and the mechanical energy of the puck 
E) the momentum and the kinetic energy of the puck

Question 4

Suppose a 70-kg student were to be compressed to form a black hole.What would be the Schwarzschild radius of this black hole? (G = 6.67 × 10^-11 N ∙ m²/kg²,c = 3.0 × 10⁸ m/s)

Accepted Answer

The answer of Suppose a 70-kg student were to be...

Question 5

The graphs shown show the magnitude F of the force exerted by a spring as a function of the distance x the spring has been stretched.For which one of the graphs does the spring obey Hooke's law? 
a)

b)

c)

d)

e)

Accepted Answer

A) Graph a 
B) Graph b 
C) Graph c 
D) Graph d 
E) Graph e

Question 6

A 1200-kg pick-up truck traveling south at 15 m/s suddenly collides with a 750-kg car that is traveling east.The two vehicles stick together and slide along the road after colliding.A highway patrol officer investigating the accident determines that the final position of the wreckage after the collision is 25 m,at an angle of 50° south of east,from the point of impact.She also determines that the coefficient of kinetic friction between the tires and the road at that location was 0.40.What was the speed of the car just before the collision?

Accepted Answer

A) 20 m/s 
B) 4.8 m/s 
C) 14 m/s 
D) 23 m/s 
E) 17 m/s

Question 7

Two identical grasshoppers jump with the same initial speed.Grasshopper A goes straight up,but grasshopper B goes up at a 66° angle above the horizontal.Assume no air resistance and choose your system to be grasshopper-Earth.Which of the following statements about these grasshoppers are correct? (There could be more than one correct choice.)

Accepted Answer

A) At their highest point, both systems have the same amount of gravitational potential energy. 
B) At their highest point, both systemshave the same amount of kinetic energy. 
C) At their highest point, both systemshave the same amount of mechanical energy. 
D) At their highest point, grasshopper B is moving faster than grasshopper A. 
E) At their highest point, the system grasshopper A-Earth has more gravitational potential energy than the system grasshopper B-Earth.

Question 8

A projectile is shot straight up from the surface of Earth by means of a very powerful cannon and experiences no appreciable air resistance.If the projectile reaches a height of 35,000 m above Earth's surface,what was the speed of the projectile when it left the cannon? (G = 6.67 × 10-11 N ∙ m2/kg2,the radius of Earth is 6.38 × 106 m,and Mearth = 5.97 ∙ 1024 kg)

Accepted Answer

A) 355 m/s 
B) 505 m/s 
C) 827 m/s 
D) 710 m/s 
E) 906 m/s

Question 9

A girl throws a stone from a bridge.Consider the following ways she might throw the stone.The speed of the stone as it leaves her hand is the same in each case. Case A: Thrown straight up.
Case B: Thrown straight down.
Case C: Thrown out at an angle of 45° above horizontal.
Case D: Thrown straight out horizontally.
In which case will the speed of the stone be greatest when it hits the water below if there is no significant air resistance?

Accepted Answer

A) Case A 
B) Case B 
C) Case C 
D) Case D 
E) The speed will be the same in all cases.

Question 10

In the figure,determine the character of the collision.The masses of the blocks,and the velocities before and after,are shown.The collision is

Accepted Answer

A) perfectly elastic. 
B) partially inelastic. 
C) completely inelastic. 
D) characterized by an increase in kinetic energy. 
E) not possible because momentum is not conserved.

Question 11

In an inelastic collision involving an isolated system,the final total momentum is

Accepted Answer

A) exactly the same as the initial momentum. 
B) more than the initial momentum. 
C) less than the initial momentum.

Question 12

A railroad car collides with and sticks to an identical railroad car that is initially at rest.After the collision,the kinetic energy of the system

Accepted Answer

A) is the same as before. 
B) is half as much as before. 
C) is one third as much as before. 
D) is one fourth as much as before. 
E) is one quarter as much as before.

Question 13

If a stone is dropped so that the initial gravitational potential energy of the system stone-Earth is 100 J but it reaches the ground with a kinetic energy of only 75 J,this is a violation of the principle of conservation of energy.

Accepted Answer

A) True 
 B)False

Question 14

A 7.5-kg otter slides down a hill,starting from rest at the top.The sloping surface of the hill is 8.8 m long,and the top is 6.5 m above the base.If the speed of the otter at the bottom of the hill is 9.2 m/s,how much energy of the otter-Earth system was converted to internal energy?

Accepted Answer

The answer of A 7.5-kg otter slides down a hill,starting...

Question 15

If a quantity you calculated had units of kg ∙ m/s,what type of quantity could it be? (There could be more than one correct choice.)

Accepted Answer

A) momentum 
B) kinetic energy 
C) work 
D) impulse 
E) force

Question 16

A 1500-kg car moving at 25 m/s hits an initially uncompressed horizontal ideal spring with spring constant (force constant)of 2.0 × 106 N/m.What is the maximum distance the spring compresses?

Accepted Answer

A) 0.17 m 
B) 0.34 m 
C) 0.51 m 
D) 0.68 m

Question 17

A block slides down a frictionless inclined ramp.If the ramp angle is 17.0° above the horizontal and the length of the surface of the ramp is $20.0 \mathrm {~m}$ find the speed of the block as it reaches the bottom of the ramp,assuming it started sliding from rest at the top.Also assume no air resistance.

Accepted Answer

A) 10.7 m/s 
B) 114 m/s 
C) 7.57 m/s 
D) 19.6 m/s

Question 18

A 60-kg skier pushes off the top of a frictionless hill with an initial speed of 4.0 m/s.How fast will she be moving after dropping 10 m in elevation? Air resistance is negligible.

Accepted Answer

A) 0.20 km/s 
B) 15 m/s 
C) 10 m/s 
D) 0.15 km/s 
E) 49 m/s

Question 19

You throw a baseball straight up.Compare the sign of the work done by the gravitational force exerted by Earth on the object while the ball goes up with the sign of the work done by the same force while it goes down.

Accepted Answer

A) The work is positive on the way up and positive on the way down. 
B) The work is positive on the way up and negative on the way down. 
C) The work is negative on the way up and positive on the way down. 
D) The work is negative on the way up and on the way down because gravity is always downward.

Question 20

How much kinetic energy does a 0.30-kg stone have if it is thrown at $44 \mathrm {~m} / \mathrm { s } ?$

Accepted Answer

A) 290 J 
B) 580 J 
C) 440 J 
D) 510 J

Exam 7: Work and Energy

A driver,traveling at 22 m/s,slows down her 2000 kg truck to stop for a red light.What work is done on the truck by the friction force exerted by the road on the truck?

A 500-kg elevator is pulled upward by a cable that exerts a constant force of 5500 N on the elevator for a distance of 50.0 m.The elevator is the system. (a)What is the work done by the 5500-N force? (b)What is the work done by the gravitational force? (c)What is the net work done on the elevator?

On a horizontal frictionless air table,a puck runs into an ideal horizontal spring that is fastened to the table.The puck compresses the spring by 15 cm before coming to rest.During the compression process,which quantities are conserved?

Suppose a 70-kg student were to be compressed to form a black hole.What would be the Schwarzschild radius of this black hole? (G = 6.67 × 10^-11 N ∙ m²/kg²,c = 3.0 × 10⁸ m/s)

The graphs shown show the magnitude F of the force exerted by a spring as a function of the distance x the spring has been stretched.For which one of the graphs does the spring obey Hooke's law? a) b) c) d) e)

In the figure,determine the character of the collision.The masses of the blocks,and the velocities before and after,are shown.The collision is

In an inelastic collision involving an isolated system,the final total momentum is

A railroad car collides with and sticks to an identical railroad car that is initially at rest.After the collision,the kinetic energy of the system

If a stone is dropped so that the initial gravitational potential energy of the system stone-Earth is 100 J but it reaches the ground with a kinetic energy of only 75 J,this is a violation of the principle of conservation of energy.

A 7.5-kg otter slides down a hill,starting from rest at the top.The sloping surface of the hill is 8.8 m long,and the top is 6.5 m above the base.If the speed of the otter at the bottom of the hill is 9.2 m/s,how much energy of the otter-Earth system was converted to internal energy?

If a quantity you calculated had units of kg ∙ m/s,what type of quantity could it be? (There could be more than one correct choice.)

A 1500-kg car moving at 25 m/s hits an initially uncompressed horizontal ideal spring with spring constant (force constant) of 2.0 × 10⁶ N/m.What is the maximum distance the spring compresses?

A 60-kg skier pushes off the top of a frictionless hill with an initial speed of 4.0 m/s.How fast will she be moving after dropping 10 m in elevation? Air resistance is negligible.

You throw a baseball straight up.Compare the sign of the work done by the gravitational force exerted by Earth on the object while the ball goes up with the sign of the work done by the same force while it goes down.

How much kinetic energy does a 0.30-kg stone have if it is thrown at $44 \mathrm {~m} / \mathrm { s } ?$

Exam 7: Work and Energy

A driver,traveling at 22 m/s,slows down her 2000 kg truck to stop for a red light.What work is done on the truck by the friction force exerted by the road on the truck?

A 500-kg elevator is pulled upward by a cable that exerts a constant force of 5500 N on the elevator for a distance of 50.0 m.The elevator is the system. (a)What is the work done by the 5500-N force? (b)What is the work done by the gravitational force? (c)What is the net work done on the elevator?

On a horizontal frictionless air table,a puck runs into an ideal horizontal spring that is fastened to the table.The puck compresses the spring by 15 cm before coming to rest.During the compression process,which quantities are conserved?

Suppose a 70-kg student were to be compressed to form a black hole.What would be the Schwarzschild radius of this black hole? (G = 6.67 × 10-11 N ∙ m2/kg2,c = 3.0 × 108 m/s)

The graphs shown show the magnitude F of the force exerted by a spring as a function of the distance x the spring has been stretched.For which one of the graphs does the spring obey Hooke's law? a) b) c) d) e)

In the figure,determine the character of the collision.The masses of the blocks,and the velocities before and after,are shown.The collision is

In an inelastic collision involving an isolated system,the final total momentum is

A railroad car collides with and sticks to an identical railroad car that is initially at rest.After the collision,the kinetic energy of the system

If a stone is dropped so that the initial gravitational potential energy of the system stone-Earth is 100 J but it reaches the ground with a kinetic energy of only 75 J,this is a violation of the principle of conservation of energy.

A 7.5-kg otter slides down a hill,starting from rest at the top.The sloping surface of the hill is 8.8 m long,and the top is 6.5 m above the base.If the speed of the otter at the bottom of the hill is 9.2 m/s,how much energy of the otter-Earth system was converted to internal energy?

If a quantity you calculated had units of kg ∙ m/s,what type of quantity could it be? (There could be more than one correct choice.)

A 1500-kg car moving at 25 m/s hits an initially uncompressed horizontal ideal spring with spring constant (force constant) of 2.0 × 106 N/m.What is the maximum distance the spring compresses?

A 60-kg skier pushes off the top of a frictionless hill with an initial speed of 4.0 m/s.How fast will she be moving after dropping 10 m in elevation? Air resistance is negligible.

You throw a baseball straight up.Compare the sign of the work done by the gravitational force exerted by Earth on the object while the ball goes up with the sign of the work done by the same force while it goes down.

How much kinetic energy does a 0.30-kg stone have if it is thrown at 44 m/s?44 \mathrm {~m} / \mathrm { s } ?44 m/s?

Suppose a 70-kg student were to be compressed to form a black hole.What would be the Schwarzschild radius of this black hole? (G = 6.67 × 10^-11 N ∙ m²/kg²,c = 3.0 × 10⁸ m/s)

A 1500-kg car moving at 25 m/s hits an initially uncompressed horizontal ideal spring with spring constant (force constant) of 2.0 × 10⁶ N/m.What is the maximum distance the spring compresses?

How much kinetic energy does a 0.30-kg stone have if it is thrown at $44 \mathrm {~m} / \mathrm { s } ?$