Hot Seat
Review Game
1. The unit for work is Joules. What is
an equivalent unit for work using
meters, kilograms, and seconds?
a) kg m/s2
b) kg m2/s
c) kg m2/s2
d) kg2m/s2
c) kg m2/s2
2. If Zippy pushes a stationary brick
wall ten times harder than he did
yesterday, what happens to the
work done? (Increase, Decrease
or Stay the same.)
Stay the same
3. An 8.0 kg mass is moving with a
speed of 2.0 m/s. A 2.0 kg mass is
moving with speed 4.0 m/s. Both
objects encounter the same constant
braking force and are brought to rest.
How do their stopping distances
compare?
They are the same.
ΔKE = W
½ 8(2)2 = Fd
16/F = d
ΔKE = W
½ 2(4)2 = Fd
16/F = d
4. An object hits a wall and
bounces back with one-third its
original speed. What is the ratio
of the final kinetic energy to the
initial kinetic energy?
1/9
5. At what rate is a 50 kg boy using
energy when he runs up a flight of
stairs 8 m high in 6 seconds?
653 W
P = W/t
P = ∆E/t
P = mgh/t
P = 50(9.8)(8)/6
6. A 10 kg mass is moving with a
speed of 5.0 m/s. How much
work is required to stop the
mass?
125 J
W = ΔKE = ½
2
mv
=½
2
(10)(5 )
7. You slam on the brakes of your car
and skid a certain distance. If you
had been traveling three times as
fast, what distance would the car
have skidded under the same
conditions?
Nine times farther.
8. An object that has kinetic energy must
have: (mark all that apply)
a)
b)
c)
d)
Momentum
Acceleration
A net force applied to it
Potential Energy
a) Momentum
9. An apple falls from a tree. Compare its
kinetic energy to its potential energy
as it falls.
a) KE increases and PE decreases
b) KE decreases and PE decreases
c) KE increases and PE increases
d) KE decreases and PE increases
a) KE increases and PE decreases
10. A car moves twice as fast as a
truck and has half the mass of the
truck. What is the ratio of the car’s
kinetic energy to the truck’s kinetic
energy?
2 to 1
11. A lightweight object and a very
heavy object are sliding with equal
speeds along a level frictionless
surface. They both slide up the
same frictionless hill. Which rises
to a greater height?
They rise to the same height.
12. A 5.0 kg ball falls to the floor.
When it is 0.80 m above the floor,
its potential energy exactly equals
its kinetic energy. How fast is it
moving?
3.96 m/s
13. A ball falls from the top of a
building through the air (air friction
is present) to the ground below.
How does the KE just before
striking the ground compare to the
PE at the top of the building?
PEmax > KEmax
14. How many joules of energy are
used by a 2.0 hp motor that runs
for 1.0 hr? (1 hp = 746 W)
5,371,200 J
15. If a skater’s speed increases so
he has twice the momentum, then
his kinetic energy increases by
what factor?
Four
16. Consider molecules of hydrogen
gas and molecules of heavier
oxygen gas that have the same
kinetic energy. Which molecules
have a greater speed?
hydrogen gas