6. A ball is tossed from an upper-story window of a building. The ball is given

Question

6. A ball is tossed from an upper-story window of a building. The ball is given an initial velocity of 9.20 m/s at an angle of 21.0° below the horizontal. It strikes the ground 5.00 s later.

(a) How far horizontally from the base of the building does the ball strike the ground?
  m
(b) Find the height from which the ball was thrown.
m
(c) How long does it take the ball to reach a point 10.0 m below the level of launching?
s

2. Young David who slew Goliath experimented with slings before tackling the giant. He found that he could revolve a sling of length 0.700 m at the rate of 7.00 rev/s. If he increased the length to 1.000 m, he could revolve the sling only 5.00 times per second.

(a) What is the speed of the stone for each rate of rotation?
m/s at 7.00 rev/s
m/s at 5.00 rev/s

(b) What is the centripetal acceleration of the stone at 7.00 rev/s?
m/s2

(c) What is the centripetal acceleration at 5.00 rev/s?
m/s2

Explanation / Answer

a) x = vx t = (9.20 * cos 21) * 5

= 42.94 m

b) y = vyt + 1/2 g t2 = 9.2 * sin 21 * 5 + (1/2 * 9.80 * 52)

= 139 m

c) y = v sin 21* t + 1/2 * g t2  

10 = 9.2 * sin 21 t + 4.9 t2

4.9 t2 + 3.29 t - 10 = 0

t = 1.13 s

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