Elements of Physics, 50:750:131 Name ________________
Test 1 October 10, 2005
The working for all solutions must be shown. No credit will be
given for an answer with no working. Take g to be 9.80 m/s
2
.
1. An astronomical unit (AU) is the average distance between
Earth and the Sun, approximately 1.50 x 10
8
km. The speed of
light is about 3.0 x 10
8
m/s. Express the speed of light in
astronomical units per minute.
(Perhaps a more interesting question is how long it takes light to
travel one astronomical unit. The answer is just one over this
result:
1 / (0.12 A.U./min) = 8.33 min = 8 min and 20 sec
This is the time light takes to travel from the Sun to the Earth.)
2. A key falls from a bridge that is 50 m above the water. It falls
directly into a model boat, moving with constant velocity, that is
15 m from the point of impact when the key is released. What is
the speed of the boat?
The time taken by the key to fall is found from
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The boat must travel 15m in this time, so its speed is
15m/3.194s = 4.696 m/s.
3. At the instant the traffic light turns green, an automobile starts
with a constant acceleration a of 2.0 m/s
2
. At the same instant a
truck, traveling with a constant speed of 9.0 m/s, overtakes and
passes the automobile. (a) How far beyond the traffic signal will
the automobile overtake the truck? (b) How fast will the
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 Fall '08
 rollino
 Physics, Force, Work, Velocity, m/s, Astronomical unit, m/s2

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