xu (xx638) – Homework #12 – nevils – (77401)
1
This
printout
should
have
22
questions.
Multiplechoice questions may continue on
the next column or page – find all choices
before answering.
001 (part 1 of 2) 10.0 points
When a 1 kg baseball is hit,
its velocity
changes from 21 m
/
s to

27 m
/
s.
What is the magnitude of the impulse de
livered by the bat to the ball?
Answer in units of N
·
s.
002 (part 2 of 2) 10.0 points
If the baseball is in contact with the bat for
1
.
9 ms, what is the average force exerted by
the bat on the ball?
Answer in units of kN.
003 (part 1 of 2) 10.0 points
The great limestone caverns were formed by
dripping water.
The acceleration of gravity is 9
.
81 m
/
s
2
.
If water droplets of 0
.
25 mL fall from a
height of 10 m at a rate of 20 per minute, what
is the average force exerted on the limestone
floor by the droplets of water during a 18 min
period?
Answer in units of N.
004 (part 2 of 2) 10.0 points
This force is what multiple of the weight of a
water droplet?
005
10.0 points
A machine gun fires 33
.
5 g bullets at a speed
of 757 m
/
s. The gun fires 317 bullets
/
min.
What is the average force the shooter must
exert to keep the gun from moving?
Answer in units of N.
006
10.0 points
A(n) 70 kg man, standing erect, steps off a
3
.
5 m high diving platform and begins to fall
from rest. The man comes to rest 2
.
5 s after
reaching the water.
The acceleration of gravity is 9
.
8 m
/
s
2
.
What average force did the water exert on
him?
Answer in units of N.
007
10.0 points
A uranium nucleus
238
U may stay in one piece
for billions of years, but sooner or later it de
cays into an
α
particle of mass 6
.
64
×
10
−
27
kg
and
234
Th nucleus of mass 3
.
88
×
10
−
25
kg,
and the decay process itself is extremely fast
(it takes about 10
−
20
s). Suppose the uranium
nucleus was at rest just before the decay.
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 Spring '08
 None
 Friction, Mass, Work, kg, Xu

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