Chapter 5 Pretest

1. Which of the following energy forms is associated with an object’s interaction with the environment? A) potential energy, B) mechanical energy, C) nonmechanical energy, D) kinetic energy.

1. Which of the following energy forms is associated with an object’s interaction with the environment? A) potential energy, B) mechanical energy, C) nonmechanical energy, D) kinetic energy.

2. Work is done when:a. the displacement is not zerob. the displacement is zeroc. the force is zero d. the force and displacement are perpendicular

2. Work is done when:a. the displacement is not zerob. the displacement is zeroc. the force is zero d. the force and displacement are perpendicular

3. Which of the following energy forms is the sum of kinetic energy and all forms of potential energy?a. total energyb. sum energyc. nonmechanical energyd. mechanical energy

3. Which of the following energy forms is the sum of kinetic energy and all forms of potential energy?a. total energyb. sum energyc. nonmechanical energyd. mechanical energy

4. An 80.0 kg climber with a 20.0 kg pack climbs 8848 m to the top of Mount Everest. What is the climber’s potential energy?

a. 6.94 x 106 Jb. 4.16 x 106 Jc. 2.47 x 106 Jd. 1.00 x 106 J

4. An 80.0 kg climber with a 20.0 kg pack climbs 8848 m to the top of Mount Everest. What is the climber’s potential energy?

a. 6.94 x 106 Jb. 4.16 x 106 Jc. 2.47 x 106 Jd. 1.00 x 106 J

5. A bobsled zips down an ice track starting at 150 m vertical distance up the hill. Disregarding friction, what is the velocity of the bobsled at the bottom of the hill? a. 27 m/sb. 36 m/sc. 45 m/sd. 54 m/s

5. A bobsled zips down an ice track starting at 150 m vertical distance up the hill. Disregarding friction, what is the velocity of the bobsled at the bottom of the hill? a. 27 m/sb. 36 m/sc. 45 m/sd. 54 m/s

6. What is the average power supplied by a 60.0 kg secretary running up a flight of stairs rising vertically 4.0 m in 4.2 s?a. 380 Wb. 560 Wc. 610 Wd. 670 W

6. What is the average power supplied by a 60.0 kg secretary running up a flight of stairs rising vertically 4.0 m in 4.2 s?a. 380 Wb. 560 Wc. 610 Wd. 670 W

1. Demarco Murray (100 kg) accelerates from rest to 9.0 m/s in 1.5 s. What is the average power output of Demarco in kW?

F = maF = 100(9/1.5) = 600 Nd = ½ at2 d = ½ (9/1.5)(1.5)2 = 6.75 mP = Fd/tP = 600(6.75)/1.5P = 2700 W = 2.7 kW

OR P = FvThe force is still 600 N, v is the average velocity 9/2 = 4.5 m/s.P = 600 x 4.5 m/sP = 2700 W = 2.7 kW

2. Two men push a car with a horizontal force of 250 N each for a distance of 10.0 m. If a frictional force of 180 N acts in the opposite direction, what is the net work done on the car?

W = Fnet x dW = (250 + 250 – 180)10

W = 3200 J

3. A 10 kg monkey with a 1 kg banana climbs to the top of a 10 m palm tree. What is the monkey’s potential energy?

PE = mghPE = 10(10)10PE = 1000 J

4. A 25 kg skier starts from rest and moves down a 30° incline. At the bottom of the run he is a vertical distance of 110 m below his starting point. If there is no friction between his skis and the snow, what is his velocity at the bottom of the incline?

PE = KEmgh = ½ mv2

gh = ½ v2

10(110) = ½ v2

v = 46.9 m/s

5. A bowling ball starts from rest and rolls to a speed of 40 m/s down a slope 20.0° above the horizontal. Disregarding friction, what is the minimum distance it must travel to reach this speed?

PE = KEmgh = ½ mv2

gh = ½ v2

10h = ½ 402

h = 80 m (continued)

80 m is the vertical distance, which is the opposite. The distance it rolls is the hypotenuse.

sin 20° = 80/hh = 234 m

6. How is work related to force and displacement?

Work = force x displacementW = F x d

7. A skier with a mass of 88 kg hits a ramp of snow at 16 m/s and becomes airborne. At the highest point of flight, the skier is 3.7 m above ground. What is the skier’s gravitational potential energy at this point?

PE = mghPE = 88(10)3.7PE = 3256 J