Question 1

A toy rocket, weighing 10. N, blasts off from ground level. At the exact top of its trajectory, its energy is 140. J. To what vertical height does it rise?

Accepted Answer

A)  1.4 km 
B)  1.4 m 
C)  0.12 km 
D)  12. m 
E)  14. m 
A)  1.4 km 
B)  1.4 m 
C)  0.12 km 
D)  12. m 
E)  14. m

Question 2

NOTE: The following question(s) refer(s) to the Cyclone, the famous roller coaster ride at Coney Island, shown in the sketch. Assume no friction.
  
-Refer to Figure 5-6. If the roller coaster leaves point Q from rest, what is its speed at point S (at the top of the 25. m peak) compared to its speed at point R?

Accepted Answer

A)  zero 
B) 
  
C)  1/
  
D)  2 
E)  4 
A)  zero 
B) 
  
C)  1/
  
D)  2 
E)  4

Question 3

A 30. N stone is dropped from a height of 10. m, and strikes the ground with a velocity of 13. m/s. What average force of air friction acts on it as it falls?

Accepted Answer

A)  4.1 N 
B)  2.9 N 
C)  0.13 KN 
D)  7.2 N 
E)  1.2 N 
A)  4.1 N 
B)  2.9 N 
C)  0.13 KN 
D)  7.2 N 
E)  1.2 N

Question 4

The work energy theorem says

Accepted Answer

A)  the net work done plus the initial kinetic energy is the final kinetic energy. 
B)  final kinetic energy plus the net work done is the initial kinetic energy. 
C)  the net work done plus the final kinetic energy is the initial kinetic energy. 
D)  the net work done minus the initial kinetic energy is the final kinetic energy. 
E)  the net work done is equal to the initial kinetic energy less the final energy. 
A)  the net work done plus the initial kinetic energy is the final kinetic energy. 
B)  final kinetic energy plus the net work done is the initial kinetic energy. 
C)  the net work done plus the final kinetic energy is the initial kinetic energy. 
D)  the net work done minus the initial kinetic energy is the final kinetic energy. 
E)  the net work done is equal to the initial kinetic energy less the final energy.

Question 5

Problems involving a non-conservative force cannot be solved because there is no definable potential energy.

Accepted Answer

A) True 
 B)False

Question 6

A 4-kg mass moving with speed 2 m/s, and a 2-kg mass moving with a speed of 4 m/s, are gliding over a horizontal frictionless surface. Both objects encounter the same horizontal force, which directly opposes their motion, and are brought to rest by it. Which statement correctly describes the situation?

Accepted Answer

A)  Both masses travel the same distance before stopping. 
B)  The 2-kg mass travels farther, but not necessarily twice as far. 
C)  The 2-kg mass travels twice as far as the 4-kg mass before stopping. 
D)  The 4-kg mass loses more kinetic energy than the 2-kg mass. 
E)  The 4-kg mass travels twice as far as the 2-kg mass before stopping. 
A)  Both masses travel the same distance before stopping. 
B)  The 2-kg mass travels farther, but not necessarily twice as far. 
C)  The 2-kg mass travels twice as far as the 4-kg mass before stopping. 
D)  The 4-kg mass loses more kinetic energy than the 2-kg mass. 
E)  The 4-kg mass travels twice as far as the 2-kg mass before stopping.

Question 7

When you lift a 12. ounce beverage can from the table top to your mouth, you do approximately how much work?

Accepted Answer

A)  1 Calorie 
B)  1 erg 
C)  1 Watt 
D)  1 Kw-h 
E)  1 Joule 
A)  1 Calorie 
B)  1 erg 
C)  1 Watt 
D)  1 Kw-h 
E)  1 Joule

Question 8

You lift a 10. lb physics book up in the air a distance of 1 ft, at a constant velocity of 0.5 ft/s. The work done by gravity is

Accepted Answer

A)  +10 ft.lb. 
B)  +5 ft.lb. 
C)  -5 ft.lb. 
D)  -10 ft.lb. 
E)  zero. 
A)  +10 ft.lb. 
B)  +5 ft.lb. 
C)  -5 ft.lb. 
D)  -10 ft.lb. 
E)  zero.

Question 9

What is the minimum energy needed to lift 1.0 kg to a height of 200. km and to give it a speed of 8.0 km/s? (Neglect the small decrease of "g" over that distance.)

Accepted Answer

A)  34. MJ 
B)  34. kJ 
C)  34. J 
D)  34. GJ 
E)  34. TJ 
A)  34. MJ 
B)  34. kJ 
C)  34. J 
D)  34. GJ 
E)  34. TJ

Question 10

You throw a ball straight up. Compare the sign of the work done by gravity while the ball goes up with the sign of the work done by gravity while it goes down.

Accepted Answer

A)  Work up is +, and the work down is -. 
B)  Work up is -, and the work down is -. 
C)  Work up is +, and the work down is +. 
D)  Work up is -, and the work down is +. 
A)  Work up is +, and the work down is -. 
B)  Work up is -, and the work down is -. 
C)  Work up is +, and the work down is +. 
D)  Work up is -, and the work down is +.

Question 11

A 4.0 kg box of fruit slides 8.0 m down a ramp, inclined at 30.° from the horizontal. If the box slides at a constant velocity of 5.0 m/s, the work done by gravity is

Accepted Answer

A)  0.16 kJ. 
B)  -0.16 kJ. 
C)  -78. J. 
D)  zero. 
E)  +78. J. 
A)  0.16 kJ. 
B)  -0.16 kJ. 
C)  -78. J. 
D)  zero. 
E)  +78. J.

Question 12

If both the mass and the velocity of a ball are tripled, the kinetic energy is increased by a factor of

Accepted Answer

A)  6. 
B)  9. 
C)  18. 
D)  81. 
E)  27. 
A)  6. 
B)  9. 
C)  18. 
D)  81. 
E)  27.

Question 13

The total mechanical energy of a system

Accepted Answer

A)  is either all kinetic energy or all potential energy, at any one instant. 
B)  can never be negative. 
C)  is equally divided between kinetic energy and potential energy. 
D)  is constant only if nonconservative forces act. 
E)  is constant only if conservative forces act. 
A)  is either all kinetic energy or all potential energy, at any one instant. 
B)  can never be negative. 
C)  is equally divided between kinetic energy and potential energy. 
D)  is constant only if nonconservative forces act. 
E)  is constant only if conservative forces act.

Question 14

A 200-g mass attached to the end of a spring causes it to stretch 5.0 cm. If another 200-g mass is added to the spring, the potential energy of the spring will be

Accepted Answer

A)  4 times as much. 
B)  the same. 
C)    times as much. 
D)  twice as much. 
E)  3 times as much. 
A)  4 times as much. 
B)  the same. 
C)    times as much. 
D)  twice as much. 
E)  3 times as much.

Question 15

State the law of the conservation of mechanical energy.

Accepted Answer

In a conservative system, the

Question 16

My 5.0 hp mower would be equivalent to an electric mower rated at what power?

Accepted Answer

A)  0.78 KW 
B)  2.8 W 
C)  3.7 KW 
D)  0.25 KW 
E)  2.8 KW 
A)  0.78 KW 
B)  2.8 W 
C)  3.7 KW 
D)  0.25 KW 
E)  2.8 KW

Question 17

A skier, of mass 60. kg, 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?

Accepted Answer

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

Question 18

On a plot of F vs. x, what represents the work done by the force F?

Accepted Answer

A)  the length of the curve 
B)  the slope of the curve 
C)  the maximum F times minimum x 
D)  the product of the maximum force times the maximum x 
E)  the area under the curve 
A)  the length of the curve 
B)  the slope of the curve 
C)  the maximum F times minimum x 
D)  the product of the maximum force times the maximum x 
E)  the area under the curve

Question 19

Define mechanical work.

Accepted Answer

Mechanically, work involves fo

Question 20

An auto is coasting on a level road. It weighs 10. kN. How much work is done by gravity as it moves horizontally 150. meters?

Accepted Answer

zero (disp

Exam 5: Work and Energy

A toy rocket, weighing 10. N, blasts off from ground level. At the exact top of its trajectory, its energy is 140. J. To what vertical height does it rise?

A 30. N stone is dropped from a height of 10. m, and strikes the ground with a velocity of 13. m/s. What average force of air friction acts on it as it falls?

The work energy theorem says

Problems involving a non-conservative force cannot be solved because there is no definable potential energy.

When you lift a 12. ounce beverage can from the table top to your mouth, you do approximately how much work?

You lift a 10. lb physics book up in the air a distance of 1 ft, at a constant velocity of 0.5 ft/s. The work done by gravity is

What is the minimum energy needed to lift 1.0 kg to a height of 200. km and to give it a speed of 8.0 km/s? (Neglect the small decrease of "g" over that distance.)

You throw a ball straight up. Compare the sign of the work done by gravity while the ball goes up with the sign of the work done by gravity while it goes down.

A 4.0 kg box of fruit slides 8.0 m down a ramp, inclined at 30.° from the horizontal. If the box slides at a constant velocity of 5.0 m/s, the work done by gravity is

If both the mass and the velocity of a ball are tripled, the kinetic energy is increased by a factor of

The total mechanical energy of a system

A 200-g mass attached to the end of a spring causes it to stretch 5.0 cm. If another 200-g mass is added to the spring, the potential energy of the spring will be

State the law of the conservation of mechanical energy.

My 5.0 hp mower would be equivalent to an electric mower rated at what power?

A skier, of mass 60. kg, 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?

On a plot of F vs. x, what represents the work done by the force F?

Define mechanical work.

An auto is coasting on a level road. It weighs 10. kN. How much work is done by gravity as it moves horizontally 150. meters?

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