Physics 53
Summer 2010
Quiz 1
Solutions
Check the best answer.
1.
Ball A is thrown horizontally outward from a pier at height h above the water,
while at the same time ball B is simply dropped from rest into the water from the
same point. Neglect air resistance. Which of the following is NOT true?
At every instant until they strike the water, the two
balls are at the same height above the water.
At every instant until they strike the water, the two
balls have the same acceleration.
√
The balls strike the water with the same speed. [Ball
A is faster. They have the same vertical component
of velocity, but B has zero horizontal component.]
The balls strike the water at the same time.
Check T or F depending on whether the statement is true or false.
2.
Two vectors that are perpendicular to each other cannot add to zero.
√
T
F
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Physics 53
3.
a.
Summer 2010
A bicycle rider travels along a straight road at a constant speed of 5 m/s. Just as
she passes a golfer in a golf cart at rest, the golfer starts to accelerate at a constant
rate of 2 m/s2 to overtake her.
a.
Find the time it takes the golf cart to draw even with the bike.
b.
Find the speed of the golf cart at this time.
c.
Find how far the golf cart travels before it draws even with the bike.
For the bike: xb = 5t . For the cart: xc = 12 ⋅ 2t 2 . Set these equal: 5t = t 2 . The two roots
are t = 0 , which is when the bike passes the cart, and t = 5 s, which is when the
cart catches (and passes) the bike.
b.
For the cart: vc = 2t , so at t = 5 we have vc = 10 m/s.
c.
When t = 5 we have xc = 25 m.
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