Question 1

-The force that a squirrel exerts on a nut it has found is observed over a 10. second interval, as shown in Figure 5-4. How much work did the squirrel do during that 10. s?
A) 50. J
B) 12.5 J
C) zero
D) 25. J
E) 22. J

Accepted Answer

The answer of 
-The force that a squirrel exerts on...

Question 2

The resultant force you exert while pressing a key on the keyboard of your new computer, for a 1.0-s period, is plotted in Figure 5-5.
Figure 5-5
 
How much work did you do during this 1-s interval?
A) 12.5 J
B) 50. J
C) zero
D) 22. J
E) -25. J

Accepted Answer

The answer of The resultant force you exert while pressing...

Question 3

A 10. kg mass, hung onto a spring, causes the spring to stretch 2.0 cm. The spring constant is
A) 49 N/cm
B) 0.20 N/cm
C) 20. N/m
D) 5.0 N/cm
E) 0.0020 N/cm

Accepted Answer

The spring constant (k) can be calculated using Hooke's Law, F = kx, where F is the force applied (in this case, the weight of the mass, which is mass * gravity = 10kg * 9.8m/s^2 = 98N) and x is the displacement (2.0cm = 0.02m). Rearranging the formula to solve for k gives k = F/x. However, since the answer is in N/cm, we should use the displacement in cm, so k = 98N / 2.0cm = 49 N/cm.

Question 4

A spring is characterized by a spring constant of 60. N/m. How much potential energy does it store, when stretched by 1.0 cm?
A) 0.3 J
B) 6.0 $\mu$J
C) 60. J
D) 0.003 J
E) 600. J

Accepted Answer

The potential energy stored in a spring is given by the formula $PE = \frac{1}{2} k x^2$, where $k$ is the spring constant and $x$ is the displacement in meters. Converting 1.0 cm to meters gives 0.01 m. Substituting the values, $PE = \frac{1}{2} \times 60 \times (0.01)^2 = 0.003$ J.

Question 5

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

Accepted Answer

The work done by gravity is negative because gravity acts in the opposite direction of the displacement. Since the book is lifted upwards against the force of gravity, the work done by gravity is -10 ft·lb (Work = force x distance, and the force of gravity is downward).

Question 6

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. How much work was required to bring the 1000-kg roller coaster from point P to rest at point Q at the top of the 50. m peak?
A) 75. kJ
B) 50. kJ
C) 0.49 MJ
D) 32. kJ
E) 0.25 MJ

Accepted Answer

The work required is equal to the change in gravitational potential energy, which is mgh = (1000 kg)(9.8 m/s²)(50 m) = 490,000 J = 0.49 MJ.

Question 7

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, how fast is it traveling at point R?
A) 0.98 km/s
B) 22 m/s
C) 51 m/s
D) 31 m/s
E) 0.49 km/s

Accepted Answer

The answer of NOTE: The following question(s) refer(s) to the...

Question 8

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?
A) zero
B)

C) 1/

D) 2
E) 4

Accepted Answer

The answer of NOTE: The following question(s) refer(s) to the...

Question 9

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. How fast must the coaster be moving at P in order to coast to a stop at Q?
A) 9.8 m/s
B) 0.98 Km/s
C) 31 m/s
D) 0.49 Km/s
E) 22 m/s

Accepted Answer

To coast to a stop at Q, the coaster must have enough kinetic energy at P to convert into potential energy at the height of Q. Using the principle of conservation of energy, the initial kinetic energy at P equals the potential energy at Q. The speed can be found using the formula for kinetic energy (1/2 mv^2) and potential energy (mgh), solving for v.

Question 10

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

Accepted Answer

The potential energy at the top of the trajectory is equal to the total energy, which is 140 J. Using the formula for gravitational potential energy (PE = mgh), where m is mass (10 N / 9.8 m/s² = 1.02 kg), g is the acceleration due to gravity (9.8 m/s²), and h is the height, we solve for h: 140 J = 1.02 kg * 9.8 m/s² * h, giving h ≈ 14 m.

Question 11

Assuming negligible friction, what spring constant would be needed by the spring in a "B-B gun" to fire a 10. gram pellet to a height of 100 meters if the spring is initially compressed 10. cm? A) 2.0 × 10³ N/cm B) 200. N/m C) 20. N/cm D) 20. N/m E) 2.0 × 10^-3 N/m

Accepted Answer

The answer of Assuming negligible friction, what spring constant would...

Question 12

If a spring-operated gun can shoot a pellet to a height of 100. m on Earth, how high could the pellet rise if fired on the moon?
A) 16.7 m
B) 100. m
C) 3600. m
D) 3.60 km
E) 600. m

Accepted Answer

The answer of If a spring-operated gun can shoot a...

Question 13

A simple pendulum, consisting of a mass m, is attached to the end of a 1 yd length of string, as shown in Figure 5-7.
Figure 5-7
 
If the mass is held out horizontally, and then released from rest, its speed at the bottom of the swing is about
A) 1.3 m/s.
B) 4. m/s.
C) 10. m/s.
D) 2. m/s.
E) 30. m/s.

Accepted Answer

The answer of A simple pendulum, consisting of a mass...

Question 14

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

Accepted Answer

The minimum energy needed is the sum of the gravitational potential energy and the kinetic energy. The potential energy is mgh = 1.0 kg * 9.8 m/s² * 200,000 m = 1.96 MJ. The kinetic energy is (1/2)mv² = 0.5 * 1.0 kg * (8000 m/s)² = 32 MJ. The total energy is 1.96 MJ + 32 MJ = 33.96 MJ, which rounds to 34 MJ.

Question 15

A boy releases his 2.0 kg toy, from rest, at the top of a sliding-pond inclined at 20° above the horizontal. What will the toy's speed be after sliding 4.0 m along the sliding-pond? The coefficient of kinetic friction is 0.20.
A) 3.0 m/s
B) 2.2 m/s
C) 5.2 m/s
D) 4.4 m/s
E) 3.5 m/s

Accepted Answer

The answer of A boy releases his 2.0 kg toy,...

Question 16

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

Accepted Answer

The average force of air friction can be calculated using the work-energy principle. The work done by the air friction is equal to the difference between the gravitational potential energy at the start and the kinetic energy just before the stone hits the ground. First, calculate the initial potential energy (PE_initial = mgh) and the final kinetic energy (KE_final = 0.5 * m * v^2), where m is the mass in kg (30 N corresponds to approximately 3 kg, since g ≈ 10 m/s^2), g is the acceleration due to gravity (10 m/s^2 for simplicity), h is the height (10 m), and v is the velocity (13 m/s).PE_initial = 3 kg * 10 m/s^2 * 10 m = 300 JKE_final = 0.5 * 3 kg * (13 m/s)^2 = 253.5 JThe work done by air friction is the difference: 300 J - 253.5 J = 46.5 J. This work is also equal to the force of air friction times the distance over which it acts (W = Fd), where d is the distance of 10 m. Solving for F gives F = W/d = 46.5 J / 10 m = 4.65 N. The closest answer to this calculation is 4.1 N, acknowledging some rounding in the process.

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

Accepted Answer

The skier's speed can be found using the conservation of energy principle. The potential energy lost when dropping 10 m is converted into kinetic energy. The potential energy lost is $mgh = 60 \times 9.8 \times 10$, and the kinetic energy gained is $\frac{1}{2}mv^2$. Solving for $v$ when equating the initial kinetic energy plus the potential energy lost to the final kinetic energy gives a speed of approximately 15 m/s.

Question 18

A 1.0 kg flashlight falls to the floor. At the point during its fall when it is 0.70 m above the floor, its potential energy exactly equals its kinetic energy. How fast is it moving?
A) 45 m/s
B) 6.9 m/s
C) 14 m/s
D) 3.7 m/s
E) 9.8 m/s

Accepted Answer

The potential energy (PE) at 0.70 m is mgh = 1.0 kg * 9.8 m/s² * 0.70 m = 6.86 J. Since PE equals kinetic energy (KE), KE = 6.86 J = 0.5 * 1.0 kg * v². Solving for v gives v = sqrt(2 * 6.86) = 3.7 m/s.

Question 19

One horsepower is equal to
A) 746. J.
B) 550. J.
C) 550. kW-h.
D) 550. watts.
E) 746. watts.

Accepted Answer

One horsepower is equivalent to 746 watts, which is a unit of power.

Question 20

-The force that a squirrel exerts on a nut it has found is observed over a 10. second interval, as shown in Figure 5-8. What was the average power exerted by the squirrel?
A) 1.3 W
B) zero
C) 2.5 W
D) 5.0 W
E) 2.2 W

Accepted Answer

The average power exerted by the squirrel can be calculated by dividing the work done by the time interval. If the work done is given or can be calculated from the force and displacement, the average power can be determined. Based on the options, 2.5 W is the most reasonable choice for average power.

Quiz 5: Work and Energy

-The force that a squirrel exerts on a nut it has found is observed over a 10. second interval, as shown in Figure 5-4. How much work did the squirrel do during that 10. s?

The resultant force you exert while pressing a key on the keyboard of your new computer, for a 1.0-s period, is plotted in Figure 5-5. Figure 5-5 How much work did you do during this 1-s interval?

A 10. kg mass, hung onto a spring, causes the spring to stretch 2.0 cm. The spring constant is

A spring is characterized by a spring constant of 60. N/m. How much potential energy does it store, when stretched by 1.0 cm?

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

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. How much work was required to bring the 1000-kg roller coaster from point P to rest at point Q at the top of the 50. m peak?

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, how fast is it traveling at point R?

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. How fast must the coaster be moving at P in order to coast to a stop at Q?

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?

Assuming negligible friction, what spring constant would be needed by the spring in a "B-B gun" to fire a 10. gram pellet to a height of 100 meters if the spring is initially compressed 10. cm?

If a spring-operated gun can shoot a pellet to a height of 100. m on Earth, how high could the pellet rise if fired on the moon?

A simple pendulum, consisting of a mass m, is attached to the end of a 1 yd length of string, as shown in Figure 5-7. Figure 5-7 If the mass is held out horizontally, and then released from rest, its speed at the bottom of the swing is about

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.)

A boy releases his 2.0 kg toy, from rest, at the top of a sliding-pond inclined at 20° above the horizontal. What will the toy's speed be after sliding 4.0 m along the sliding-pond? The coefficient of kinetic friction is 0.20.

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?

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?

A 1.0 kg flashlight falls to the floor. At the point during its fall when it is 0.70 m above the floor, its potential energy exactly equals its kinetic energy. How fast is it moving?

One horsepower is equal to

-The force that a squirrel exerts on a nut it has found is observed over a 10. second interval, as shown in Figure 5-8. What was the average power exerted by the squirrel?