Ap Physics Worksheet With Answers Page 3
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2
3
4
5
6
7
82
Mgh
= Mgh
+ ½ kΔx
i
f
2
Mgh
- Mgh
= ½ kΔx
i
f
2
2(Mgh
- Mgh
) = kΔx
i
f
2
(2(Mgh
- Mgh
))/( Δx
) = k
i
f
k = 1180 N/m
2
19. A wheel of moment of inertia of 5.00 kg∙m
starts from rest and accelerates under a constant torque of 3.00 N∙m for 8.00 s.
What is the wheel's rotational kinetic energy at the end of 8.00 s?
τ = Iα
2
3.00 N∙m = (5.00 kg∙m
) α
α = 0.600 rad/s²
ω
= ω
+ αt = (0.600 rad/s²)(8.00 s) = 4.80 rad/s
f
i
2
2
Ek= ½ Iω
= (0.5)(5.00 kg∙m
)(4.80 rad/s)² = 57.6 J
20. A solid sphere of mass 1.0 kg and radius 0.010 m rolls with a speed of 10 m/s. How high up an inclined plane can it climb before
coming to rest?
The moment of inertia of solid sphere is:
2
I = (2/5)mr
Law of Conservation of Energy:
2
2
0.5mv
+ 0.5Iω
= mgh
We also know that v = rω
We get then:
2
2
2
h = (1/(mg))*0.5*[m + (2/5)m(r
)/(r
)]*v
with:
m = 1 kg
g = 9.81 N/kg
r = 0.01 m
v = 10 m/s
2
h = (1/(9.81))*0.5*[1 + 0.4]*10
h = (50/9.81)*[1.4] = 7.14 m
Chapter 7 – Momentum & Collisions
Multiple Choice:
21. The greatest change in momentum will be produced by a:
A. large force acting over a long time
B. small force acting over a short time
A
B
C
D
C. large force acting over a short time
D. small force acting over a long time
22. Impulse can be represented by
A. Δv/Δt
B. FΔt
A
B
C
D
C. mv
D. none of these
23. The momentum change of an object is equal to the
A. force acting on the object
B. velocity change of the object
A
B
C
D
C. impulse acting on the object
D. mass of the object times the force acting on it
24. A Ping-Pong gun fires a Ping-Pong ball out of its barrell. Compared to the impulse on the ball, the
impulse on the gun is
A. larger
A
B
C
B. smaller
C. the same
Use the diagram below to answer the next three questions (25-27).
Two blocks, A and B travelling towards each other with equal momenta on a frictionless surface,
are separated by a spring of negligible mass. The mass of block A is twice that of block B.
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