1. a 75g ball is thrown upward from a position on a bridge 69m above water. the
ID: 1629445 • Letter: 1
Question
1. a 75g ball is thrown upward from a position on a bridge 69m above water. the ball has an initial vertical velocity of 12m/s and enough horizontal speed to clear the bridge. how long after the launch of the ball does it hit the water
a.2s
b.3.9s
c.5.2s
d.12s
e.17s
2. a mass-less meter stick has a small mass of 1.0kg at 30cm. the fulcrum is at 45 cm. where should a 1.5kg mass be placed along the meter stick to balance the system about the fulcrum.
a.10cm
b.55cm
c.75cm
d.80cm
e.100cm
3.a simple pendulum with small amplitude oscillations has a period of 1.24s. if the length is doubled, the period becomes
a.10.2s
b.3.42s
c.2.94s
d.2.15s
e.1.75s
4.how long should you make a simple pendulum on earth so that it's period is 3s
a.2.23m
b.0.99m
c.0.75m
d.0.23m
e.0.05m
5. a bluray disk with radius 6cm takes 3.5s to accelerate from rest to 40rad/s. the disc weighs 55g. what is the tangential acceleration of a point on the cd edge?
a. 0.49
b.0.69
c.1.6
d.2.1
e.6
Explanation / Answer
3.
T = 2*pi*sqrt (L/g)
T2/T1 = sqrt (L2/L1)
T2 = T1*sqrt (L2/L1)
T2 = 1.24* sqrt (2*L1/L1)
T2 = 1.24*1.414 = 1.75 sec (E)
4
T = 2*pi*sqrt (L/g)
L = g*T^2/(4*pi^2)
L = 9.81*3^2/(4*pi^2) = 2.23 m (A)
5.
wf = wi + alpha*t
alpha = (wf - wi)/t
alpha = (40 - 0)/3.5 = 11.43 rad/sec^2
tangential acceleration = alpha*r
= 11.43*0.06 = 0.69 m/sec^2 (B)
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