Deck 6: Conservation of Energy

Question 1

A 2,000 kg car traveling at 30.0 mi/h skids to a stop in 60.0 meters.The force of friction during the skid is (1.0 mi/h = 0.447 m/s)

A) 4,500 N.
B) 4,200 N.
C) 3,750 N.
D) 3,000 N.
E) 2,400 N.

Answer 1

3,000 N.

Question 2

The explosion in a cannon exerts an average force of 30,000 N for L meters,the length of the cannon.The length of the cannon to shoot a 2.00 kg projectile from the cannon on the earth to the moon is

A) 2.75 km.
B) 3.01 km.
C) 3.98 km.
D) 4.26 km.
E) 5.02 km.

Answer 2

4.26 km.

Question 3

A 30.00 kg box slides up a 12.00 meters long incline at an angle of 30.00 degrees above the horizontal.Friction is negligible.The change in gravitational potential energy is

A) 2110 J.
B) 1467 J.
C) 1080 J.
D) 1764 J.
E) 760.0 J.

Answer 3

1764 J.

Question 4

A 5.00 gram bullet has a velocity of 300 m/s.It strikes a block of wood and penetrates to a distance of 2.00 cm.The average force of the block of wood on the bullet is

A) 9,340 N.
B) 11,250 N.
C) 15,200 N.
D) 19,500 N.
E) 21,400 N.

Question 5

A 20.0 kg box slides up a 12.0 m long incline at an angle of 30.0 degrees with the horizontal.A force of 150 N is applied to the box to pull it up the incline.The applied force makes an angle of 10.0 degrees to the incline and above the incline.If the incline has a coefficient of kinetic friction of 0.100,then the increase in the kinetic energy of the box is

A) 424 J.
B) 395 J.
C) 344 J.
D) 297 J.
E) 250 J.

Question 6

A horizontal force of 12 Newtons is applied to a 4.0 kg box that slides on a horizontal surface.The box starts from rest moves a horizontal distance of 10 meters and obtains a velocity of 5.0 m/s.The surface has friction.The friction force is

A) 7.0 N.
B) 6.5 N.
C) 6.0 N.
D) 5.7 N.
E) 4.9 N.

Question 7

The explosion in a cannon exerts an average force of 30,000 N for 2.00 meters.The velocity of a 2.00 kg projectile shot from the cannon is

A) 198 m/s.
B) 245 m/s.
C) 302 m/s.
D) 354 m/s.
E) 412 m/s.

Question 8

A 20.0 kg box slides down a 12.0 m long incline at an angle of 30.0 degrees with the horizontal.A force of 50.0 N is applied to the box in the upward direction.The applied force F makes an angle of 0.00 to the incline.If the incline has a coefficient of kinetic friction of 0.000,then the increase in the kinetic energy of the box is

A) 620 J.
B) 576 J.
C) 542 J.
D) 500 J.
E) 475 J.

Question 9

A 20.0 kg box slides down a 12.0 m long incline at an angle of 3.0 degrees with the horizontal.A force of 50.0 N is applied to the box to try to pull it up the incline.The applied force makes an angle of 0.00 degrees to the incline.If the incline has a coefficient of kinetic friction of 0.100,then the increase in the kinetic energy of the box is

A) 300 J.
B) 372 J.
C) 410 J.
D) 455 J.
E) 525 J.

Question 10

The graph shows the force on an object as it moves a distance x.What is the work done by the force when the object moves from 2.0 m to 8.0 m?

A) 35 J
B) 48 J
C) 50 J
D) 52 J
E) 60 J

Question 11

A 5.00 gram bullet has a velocity of 300 m/s.It strikes a block of wood and penetrates to a distance of 10.0 cm.The average force of the block of wood on the bullet is

A) 1,500 N.
B) 1,750 N.
C) 1,870 N.
D) 2,030 N.
E) 2,250 N.

Question 12

A 20.0 kg box slides down a 12.0 m long incline at an angle of 30.0 degrees with the horizontal.A force of 50.0 N is applied to the box to try to pull it up the incline.The applied force makes an angle of 10.00 degrees to the incline and above the incline.If the incline has a coefficient of kinetic friction of 0.100,then the increase in the kinetic energy of the box is

A) 203 J.
B) 275 J.
C) 300 J.
D) 392 J.
E) 425 J.

Question 13

The graph shows the force on an object as it moves a distance x.What is the work done by the force when the object moves from 0.0 m to 6.0 m?

A) 14 J
B) 12 J
C) 10 J
D) 8.0 J
E) 6.0 J

Question 14

A car traveling at 30 mph skids to a stop in 60 meters.If a car travels at 60 mph with the same skid conditions,then what is distance the car skids to come to a stop?

A) 340 m
B) 310 m
C) 260 m
D) 240 m
E) 190 m

Question 15

A 20.0 N force is applied at an angle of 40.0 degrees above the horizontal to a 4.00 kg box.The box moves a horizontal distance of 4.00 meters.Friction is negligible.The work done by the 20.0 N force is

A) 75.0 J.
B) 61.3 J.
C) 50.1 J.
D) 46.3 J.
E) 40.5 J.

Question 16

A 6.00 kg box slides up a 8.00 m long friction incline at an angle of 30.0 degrees by a force 50.0 N parallel to the incline.The coefficient of kinetic friction is 0.100.The work done against friction is

A) 22.0 J.
B) 26.5 J.
C) 30.3 J.
D) 35.2 J.
E) 40.7 J.

Question 17

A 20.0 kg box slides down a 12.0 m long incline at an angle of 30.0 degrees with the horizontal.A force of 50.0 N is applied to the box in the upward direction to try to pull it up the incline.The applied force makes an angle of 10.0 degrees to the incline.If the incline has a coefficient of kinetic friction of 0.00,then the increase in the kinetic energy of the box is

A) 420 J.
B) 475 J.
C) 521 J.
D) 585 J.
E) 620 J.

Question 18

A 20 N horizontal force is applied to a 4.0 kg box.Friction is negligible.The box moves a horizontal distance of 3.0 meters.The work done by the 20 N force is

A) 60 J.
B) 80 J.
C) 10 J.
D) 92 J.
E) 65 J.

Question 19

The most fundamental forms of energy are

A) elastic,gravitational,internal.
B) kinetic,potential,rest.
C) electromagnetic,chemical,nuclear.
D) translational,rotational,vibrational.

Question 20

A 20.0 kg box slides up a 12.0 m long incline at an angle of 30.0 degrees with the horizontal.A force of 150 N is applied to the box to pull it up the incline.The applied force makes an angle of 0.00 degrees to the incline.If the incline has a coefficient of kinetic friction of 0.100,then the increase in the kinetic energy of the box is

A) 330 J.
B) 390 J.
C) 420 J.
D) 481 J.
E) 597 J.

Question 21

A 2.00 kg pendulum bob on a string 1.50 m long,is released with a velocity of 2.00 m/s when the support string makes an angle of 30.0 degrees with the vertical.What is the velocity of the bob at the bottom of the swing?

A) 4.32 m/s
B) 4.00 m/s
C) 3.75 m/s
D) 3.04 m/s
E) 2.81 m/s

Question 22

A 3.00 kg pendulum bob on a string 2.00 m long,is released with a velocity of 2.00 m/s when the support string makes an angle of 45.0 degrees with the vertical.What is the tangential acceleration of the bob at the highest point of its motion?

A) 6.04 m/s²
B) 6.89 m/s²
C) 7.80 m/s²
D) 8.20 m/s²
E) 9.02 m/s²

Question 23

A 2.00 kg pendulum bob on a string 1.50 m long,is released with a velocity of 3.00 m/s when the support string makes an angle of 45.0 degrees with the vertical.What is the tension in the string at the bottom of the swing?

A) 53.5 N
B) 49.8 N
C) 43.1 N
D) 37.5 N
E) 30.2 N

Question 24

A 2000 kg car accelerates up to a velocity of 40 m/s in 5.0 seconds.The brakes are applied,and the car is brought to a stop.The work done by the friction in the brakes is

A) 1.0 $\times$ 10⁶ J.
B) 1.2 $\times$ 10⁶ J.
C) 1.6 $\times$ 10⁶ J.
D) 2.1 $\times$ 10⁶ J.
E) 2.5 $\times$ 10⁶ J.

Question 25

In order to conserve fuel,you modify your car by removing 100 kg of excess weight.How much energy is saved each time you accelerate from 0 to 100 km/hr (62 mph)?

A) 2.86 $\times$ 10² J
B) 2.86 $\times$ 10⁴ J
C) 3.86 $\times$ 10⁴ J
D) 3.86 $\times$ 10² J

Question 26

A 2.00 kg pendulum bob on a string 1.50 m long,is released with a velocity of 4.00 m/s when the support string makes an angle of 30.0 degrees with the vertical.What is the velocity of the bob at the bottom of the swing?

A) 4.47 m/s
B) 4.02 m/s
C) 3.75 m/s
D) 3.50 m/s
E) 2.85 m/s

Question 27

A horizontal force is applied to a 2.0 kg box.The box starts from rest,moves a horizontal distance of 12.0 meters,and obtains a velocity of 8.0 m/s.The change in the kinetic energy is

A) 32 J.
B) 48 J.
C) 50 J.
D) 58 J.
E) 64 J.

Question 28

A 120 N horizontal force is applied to a 4.00 kg box.The box moves a horizontal distance of 8.00 meters.The change in the kinetic energy of the box is

A) 960 J.
B) 875 J.
C) 821 J.
D) 765 J.
E) 633 J.

Question 29

A 2.00 kg pendulum bob on a string 2.00 m long,is released with a velocity of 1.50 m/s when the support string makes an angle of 30.0 degrees with the vertical.What is the tangential acceleration of the bob at the highest point of its motion?

A) 5.33 m/s²
B) 5.77 m/s²
C) 6.25 m/s²
D) 7.00 m/s²
E) 7.25 m/s²

Question 30

A 75.0 kg skier slides down a 75.0 m high slope without friction.The velocity of the skier at the bottom of the slope is

A) 20.6 m/s.
B) 29.7 m/s.
C) 38.3 m/s.
D) 40.5 m/s.
E) 50.0 m/s.

Question 31

A 2.00 kg pendulum bob on a string 3.00 m long is released with a velocity of 1.00 m/s when the support string makes an angle of 30.0 degrees with the vertical.What is the tension in the string at the highest point of its motion?

A) 30.8 N
B) 27.5 N
C) 20.1 N
D) 16.6 N
E) 10.5 N

Question 32

A 2.00 kg pendulum bob on a string 1.50 m long,is released with a velocity of 3.00 m/s when the support string makes an angle of 45.0 degrees with the vertical.What is the angle with the vertical the bob makes at the highest point of its motion?

A) 47.5 degrees
B) 50.0 degrees
C) 59.8 degrees
D) 66.4 degrees
E) 75.3 degrees

Question 33

As a hiker descends a hill,the work done by gravity on the hiker is

A) positive and depends on the path taken.
B) negative and depends on the path taken.
C) positive and independent of the path taken.
D) negative and independent of the path taken.

Question 34

A 20.0 kg box slides up a 12.0 m long incline at an angle of 30.0 degrees with the horizontal.A force of 150 N is applied to the box to pull it up the incline.The applied force makes an angle of 10.0 degrees to the incline.What is the change in gravitational potential energy,in Joules?

A) 2,570
B) 2,350
C) 1,450
D) 1,180
E) 945

Question 35

A 120 N force is applied at an angle of 30.0 degrees above the horizontal to a 4.00 kg box.The box moves a horizontal distance of 8.00 meters.The change in the kinetic energy of the box is

A) 667 J.
B) 750 J.
C) 831 J.
D) 890 J.
E) 920 J.

Question 36

A 2500 kg car accelerates up to a velocity of 30.0 m/s in 8.00 seconds.The work done by the engine to accelerate the car is

A) 3.10 $\times$ 10⁶ J.
B) 2.56 $\times$ 10⁶ J.
C) 2.01 $\times$ 10⁶ J.
D) 1.85 $\times$ 10⁶ J.
E) 1.13 $\times$ 10⁶ J.

Question 37

A 2.00 kg pendulum bob on a string 1.50 m long,is released with a velocity of 4.00 m/s when the support string makes an angle of 30.0 degrees with the vertical.What is the angle with the vertical the bob makes at the highest point of its motion?

A) 85.3 degrees
B) 71.2 degrees
C) 60.3 degrees
D) 56.7 degrees
E) 45.0 degrees

Question 38

A 2.00 kg pendulum bob on a string 1.50 m long is released with a velocity of 0.00 m/s when the support string makes an angle of 60.0 degrees with the vertical.What is the tension in the string at the bottom of the swing?

A) 60.4 N
B) 55.6 N
C) 50.1 N
D) 42.6 N
E) 39.2 N

Question 39

A 3.00 kg pendulum bob on a string 2.00 m long is released with a velocity of 2.00 m/s when the support string makes an angle of 45.0 degrees with the vertical.What is the tension in the string at the highest point of its motion?

A) 12.5 N
B) 17.8 N
C) 21.4 N
D) 28.9 N
E) 31.6 N

Question 40

A 5.00 kg box slides up a 10.0 m long friction incline at an angle of 20.0 degrees with the horizontal pushed by a 40.0 N force parallel to the incline.The coefficient of kinetic friction is 0.100.The change in kinetic energy is

A) 105 J.
B) 145 J.
C) 186 J.
D) 200 J.
E) 243 J.

Question 41

A spring with a spring constant of 8.0 N/m is initially compressed to 5.0 cm.The work done as it is compressed another 15 cm,to a total compression of 20 cm,is

A) 0.85 J.
B) 0.54 J.
C) 0.25 J.
D) 0.15 J.
E) 0.09 J.

Question 42

A spring with a spring constant of 8.0 N/m is compressed to 20 cm.If the spring is uncompressed initially,then the work done is

A) 0.12 J.
B) 0.16 J.
C) 0.19 J.
D) 0.22 J.
E) 0.26 J.

Question 43

An 8000 kg satellite is launched from the surface of the earth,and injected into a circular orbit at an altitude of 100 km above the surface of the earth.The gravitational potential energy of the satellite in the circular orbit is (G = 6.67 $\times$ 10^-11 Nm²/kg², Me = 5.98 $\times$ 10²⁴ kg, Re = 6.38 $\times$ 10⁶ m)

A) 5.01 $\times$ 10¹¹ J.
B) 4.92 $\times$ 10¹¹ J.
C) 4.75 $\times$ 10¹¹ J.
D) 4.02 $\times$ 10¹¹ J.
E) 3.85 $\times$ 10¹¹ J.

Question 44

An 8000 kg satellite is launched from the surface of the earth,and injected into a circular orbit at an altitude of 100 km above the surface of the earth.The kinetic energy of the satellite in the circular orbit is (G = 6.67 $\times$ 10^-11 Nm²/kg², Me = 5.98 $\times$ 10²⁴ kg, Re = 6.38 $\times$ 10⁶ m)

A) 5.02 $\times$ 10¹¹ J.
B) 4.25 $\times$ 10¹¹ J.
C) 3.45 $\times$ 10¹¹ J.
D) 2.46 $\times$ 10¹¹ J.
E) 2.01 $\times$ 10¹¹ J.

Question 45

A student lifts a weight of 10.0 N a distance of 0.500 meters.The energy needed to do this work in calories is (1 cal = 4.186 Joules)

A) 0.570 cal.
B) 0.750 cal.
C) 1.19 cal.
D) 1.75 cal.
E) 2.30 cal.

Question 46

An 8000 kg satellite is launched from the surface of the earth,and injected into outer space a long distance from the earth.The kinetic energy needed to launch the satellite into outer space is (G = 6.67 $\times$ 10^-11 Nm²/kg², Me = 5.98 $\times$ 10²⁴ kg, Re = 6.38 $\times$ 10⁶ m)

A) 5.00 $\times$ 10¹¹ J.
B) 4.03 $\times$ 10¹¹ J.
C) 3.57 $\times$ 10¹¹ J.
D) 3.00 $\times$ 10¹¹ J.
E) 2.35 $\times$ 10¹¹ J.

Question 47

A spring-powered dart gun is un-stretched and has a spring constant 16.0 N/m.The spring is compressed by 8.0 cm and a 5.0 gram projectile is placed in the gun.The kinetic energy of the projectile when it is shot from the gun is

A) 0.125 J.
B) 0.090 J.
C) 0.075 J.
D) 0.051 J.
E) 0.030 J.

Question 48

A spring-powered dart gun is un-stretched and has a spring constant 12.0 N/m.The spring is compressed by 8.00 cm and a 5.00 gram projectile is placed in the gun.The velocity of the projectile when it is shot from the gun is

A) 1.52 m/s.
B) 2.54 m/s.
C) 3.92 m/s.
D) 4.24 m/s.
E) 5.02 m/s.

Question 49

The graph shows the force on an object as it moves a distance x.What is the work done by the force when the object moves from 0.0 m to 10.0 m?

A) 34 J
B) 45 J
C) 52 J
D) 64 J
E) 75 J

Question 50

An 8000 kg satellite is launched from the surface of the earth,and injected into outer space a long distance from the earth.The initial velocity needed to launch the satellite into outer space is (G = 6.67 $\times$ 10^-11 Nm²/kg², Me = 5.98 $\times$ 10²⁴ kg, Re = 6.38 $\times$ 10⁶ m)

A) 8,450 m/s.
B) 9,200 m/s.
C) 11,180 m/s.
D) 18,900 m/s.
E) 25,200 m/s.

Question 51

A spring-powered dart gun is un-stretched and has a spring constant 16.0 N/m.The spring is compressed by 8.00 cm and a 5.00 gram projectile is placed in the gun.The velocity of the projectile when it is shot from the gun is

A) 2.04 m/s.
B) 2.75 m/s.
C) 3.50 m/s.
D) 3.75 m/s
E) 4.53 m/s.

Question 52

The graph shows the force on an object as it moves a distance x.What is the work done by the force when the object moves from 0.0 m to 4.0 m?

A) 6.0 J
B) 8.0 J
C) 10 J
D) 12 J
E) 14 J

Question 53

A spring is stretched from its equilibrium position 10 cm when a 1 kg mass is attached to it.Removing the 1 kg mass and replacing it with a 0.50 kg mass then releasing the spring,how high will the 0.50 kg mass rise above the point where it is released?

A) 0.44 m
B) 0.24 m
C) 0.80 m
D) 1.0 m

Question 54

A 200 N box is pushed up an incline that is 5.00 m long and rises 1 m.If the incline is frictionless,then the work done by the pushing force is

A) 336 J.
B) 305 J.
C) 275 J.
D) 200 J.
E) 157 J.

Question 55

A spring-powered dart gun is un-stretched and has a spring constant 150 N/m.The spring is compressed by 8.00 cm and a 5.00 gram projectile is placed in the gun.The maximum height of the projectile when it is shot at an angle of 30.0 degrees above the horizontal from the gun is

A) 5.03 m.
B) 4.24 m.
C) 3.90 m.
D) 3.20 m.
E) 2.45 m.

Question 56

In order to conserve fuel,you modify your car by removing 100 kg of excess weight.How much energy is saved each time you drive up a 3 km high mountain?

A) 2.94 $\times$ 10⁶ J
B) 2.86 $\times$ 10⁴ J
C) 3.86 $\times$ 10⁶ J
D) 3.00 $\times$ 10⁵ J

Question 57

A spring is stretched from 0.500 m to 0.800 m.Assume the un-stretched position is 0.00 m.If the spring constant of the spring is 10.0 N/m,what is the work done on the spring?

A) 1.95 J
B) 2.21 J
C) 2.45 J
D) 2.75 J
E) 3.01 J

Question 58

A spring-powered dart gun is un-stretched and has a spring constant 100 N/m.The spring is compressed by 8.00 cm and a 5.00 gram projectile is placed in the gun.The maximum height of the projectile when it is shot straight up from the gun is

A) 7.57 m.
B) 7.00 m.
C) 6.53 m.
D) 6.00 m.
E) 5.50 m.

Question 59

A 20.0 kg box slides up a 12.0 m long incline at an angle of 30.0 degrees with the horizontal.A force of 150 N is applied to the box to pull it up the incline.The applied force makes an angle of 10.0 degrees to the incline.What is the work done by the applied force,in Joules?

A) 1,870
B) 1,770
C) 1,500
D) 1,450
E) 1,380

Question 60

A 200 N box is pushed up an incline that is 5.00 m long and rises 1.00 m.The incline has a coefficient of kinetic friction of 0.200.The work done by the pushing force is

A) 475 J.
B) 422 J.
C) 356 J.
D) 300 J.
E) 396 J.

Question 61

An airplane has a mass of 30,000 kg and travels at 300 m/s.If the drag force is 1000 N,the power the engines have to provide to keep flying at a constant speed is

A) 6.0 $\times$ 10⁵ W
B) 5.5 $\times$ 10⁵ W
C) 4.9 $\times$ 10⁵ W
D) 4.2 $\times$ 10⁵ W
E) 3.0 $\times$ 10⁵ W

Question 62

An asteroid,of radius 2.1 km,is observed to have an escape speed equal to a typical person's speed attained by jumping off , 3.0 m/s.What is its mass?

A) 4.2 $\times$ 10¹⁴ kg
B) 2.8 $\times$ 10¹⁴ kg
C) 5.7 $\times$ 10¹⁴ kg
D) 0.5 $\times$ 10¹⁴ kg
E) 1.4 $\times$ 10¹⁴ kg

Question 63

A student lifts a weight of 10.0 N a distance of 0.5 meters.If this exercise is repeated 50 times in 100 seconds,then the power of this exercise is

A) 2.5 Watts.
B) 3.1 Watts.
C) 3.6 Watts.
D) 4.0 Watts.
E) 4.8 Watts.

Question 64

A 2500 kg car accelerates from rest to a velocity of 10 m/s in 5.0 seconds.The power of the engine during this acceleration is

A) 50 kW.
B) 47 kW.
C) 40 kW.
D) 31 kW.
E) 25 kW.

Question 65

A car has a mass of 2,000 kg and travels at 20.0 m/s.If the drag force is 100 N,the power the engines have to provide to keep moving at constant speed is

A) 2.0 kW.
B) 2.9 kW.
C) 3.4 kW.
D) 3.9 kW.
E) 4.2 kW.

Question 66

A comet is observed to pass 1.50 $\times$ 10⁸ m from the surface of the sun.The sun's radius is 6.96 $\times$ 10⁸ m.What is the speed of the comet at this point,if its speed when passing the Earth's orbit,1.50 $\times$ 10¹¹ m from the sun's center,is 25km/s?

A) 561 km/s
B) 618 km/s
C) 562 km/s
D) 585 km/s

Question 67

A blob of clay,mass M,is propelled upward from a spring that is initially compressed by an amount d.If,upon its release,the clay reaches an ultimate height of h above the unstretched spring's end,what is the spring constant k?

A) kd²/(mg)
B) kd²/(2mg)- d
C) kd²/(mg)-d
D) kd²/(2mg)

Question 68

A 1800 kg car moving at 20 m/s hits an initially uncompressed spring with a spring constant of 2.0 $\times$ 10⁶ N/m.The maximum compression of the spring is

A) 0.40 m.
B) 0.60 m.
C) 0.80 m.
D) 1.0 m.
E) 1.2 m.

Question 69

A 1.1 kg seagull takes off from a piling along the California coast and accelerates within 0.50s to a flight speed of 7.5m/s along a horizontal path.What average power was developed by the bird's wings as it accelerated?

A) 62W
B) 8.3W
C) 33W
D) 250W

Question 70

An asteroid,of mass 1.4 $\times$ 10¹⁴ kg is observed to have an escape speed equal to a typical person's speed attained by jumping off,3.0m/s.What is its radius?

A) 6.3 km
B) 2.1 km
C) 1.0 km
D) 0.5 km

Question 71

A ski lift carries passengers up a 150 m high slope at the rate of one chair every 30.0 seconds.If the chair will hold two passengers with a total mass of 190 kg,then the power of the engine that powers the ski lift is

A) 6.96 kW.
B) 7.83 kW.
C) 8.75 kW.
D) 9.31 kW.
E) 9.90 kW.

Question 72

A dragster drives a quarter mile (402 m)at a constant rate of acceleration,starting from rest and finishing the race at a final speed of 450 km/hr.If the mass of the dragster is 975 kg,together with its driver,and rolling friction is ignored,what average power was developed by the engine,if 50% of the power developed by the engine was delivered to the wheels?

A) 4.7 MW
B) 1.2 MW
C) 0.6 MW
D) 2.4 MW

Question 73

A 2000 kg car accelerates from rest to a velocity of 20 m/s in 10 seconds.The power of the engine during this acceleration is

A) 50 kW.
B) 40 kW.
C) 30 kW.
D) 20 kW.
E) 10 kW.

Question 74

A blob of clay,mass M,is dropped onto a spring from a height h above the end of the spring.If the spring compresses an amount d as the blob comes to rest,what is the spring constant?

A) 2mgh/d²
B) mgh/d²
C) mg(h+d)/d²
D) 2mg(h+d)/d²

Question 75

During a basketball game,a player shoots a ball from half-court.When the ball reaches a height of 4.5 m above the floor,it is moving at 5.0 m/s.Assuming the shot was perfectly made,it will pass through the rim of the basket,3.05 m above the floor.How fast the ball moving when it passes through the rim?

A) 7.7 m/s
B) 7.3 m/s
C) 9.2 m/s
D) 5.3 m/s

Question 76

A road bicycle racer rides down the highway from Pike's peak.During one stretch of the ride,he descends 150 m while accelerating from 35 km/hr to some final speed.Assuming rolling friction and air resistance to be negligible,what is that final speed?

A) 113 km/h
B) 118 km/h
C) 148 km/h
D) 169 km/h

Question 77

A spring-powered dart gun is un-stretched and has a spring constant 10.0 N/m.The spring is compressed by 8.00 cm and a 5.00 gram projectile is placed in the gun.The kinetic energy of the projectile when it is shot from the gun is

A) 0.020 J.
B) 0.032 J.
C) 0.060 J.
D) 0.100 J.
E) 0.120 J.

Question 78

A 90.0 kg person is running up the stairs at 0.500 m/s.The power needed to run up the stairs is

A) 441 Watts.
B) 395 Watts.
C) 302 Watts.
D) 275 Watts.
E) 257 Watts.

Question 79

A 1.1 kg seagull takes off from a piling along the California coast and accelerates within 0.50 s to a flight speed of 7.5 m/s along a slightly inclined path.At the end of the 0.50 s period,it is 5.3 m above its point of takeoff.What power was developed by the bird's wings?

A) 180 W
B) 110 W
C) 52 W
D) 62 W

Question 80

If the escape speed of a star is equal to the speed of light,its radius is the so-called Schwarzschild radius.What is the Schwarzschild radius of the sun,whose mass is 2.0 $\times$ 10³⁰ kg?

A) 4.5 km
B) 1.5 km
C) 5.9 km
D) 3.0 km