Transcript 05 Pretest answers

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
zero
b. the displacement is zero
c. the force is zero
d. the force and
displacement are
perpendicular
2. Work is done when:
a. the displacement is not
zero
b. the displacement is zero
c. 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 energy
b. sum energy
c. nonmechanical energy
d. mechanical energy
3. Which of the following energy
forms is the sum of kinetic
energy and all forms of potential
energy?
a. total energy
b. sum energy
c. nonmechanical energy
d. 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.
b.
c.
d.
6.94 x 106 J
4.16 x 106 J
2.47 x 106 J
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.
b.
c.
d.
6.94 x 106 J
4.16 x 106 J
2.47 x 106 J
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/s
b. 36 m/s
c. 45 m/s
d. 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/s
b. 36 m/s
c. 45 m/s
d. 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 W
b. 560 W
c. 610 W
d. 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 W
b. 560 W
c. 610 W
d. 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 = ma
F = 100(9/1.5) = 600 N
2
d = ½ at
d = ½ (9/1.5)(1.5)2 = 6.75 m
P = Fd/t
P = 600(6.75)/1.5
P = 2700 W = 2.7 kW
OR
P = Fv
The force is still 600 N,
v is the average
velocity 9/2 = 4.5 m/s.
P = 600 x 4.5 m/s
P = 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 d
W = (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 = mgh
PE = 10(10)10
PE = 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 = KE
2
mv
mgh = ½
2
gh = ½ v
2
10(110) = ½ v
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 = KE
2
mv
mgh = ½
2
gh = ½ v
2
10h = ½ 40
h = 80 m (continued)
80 m is the vertical
distance, which is the
opposite. The distance it
rolls is the hypotenuse.
sin 20° = 80/h
h = 234 m
6. How is work
related to
force and
displacement?
Work = force x
displacement
W=Fxd
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 = mgh
PE = 88(10)3.7
PE = 3256 J