1.A baseball is hit so that it travels straight upward after being struck by the
ID: 1880223 • Letter: 1
Question
1.A baseball is hit so that it travels straight upward after being struck by the bat. A fan observes that it takes 3.20 s for the ball to reach its maximum height.
(a) Find the ball's initial velocity.
m/s upward
(b) Find the height it reaches.
2.A bullet is fired through a board 8.0 cm thick in such a way that the bullet's line of motion is perpendicular to the face of the board. The initial speed of the bullet is 300 m/s and it emerges from the other side of the board with a speed of 200 m/s.
(a) Find the acceleration of the bullet as it passes through the board.
m/s2
(b) Find the total time the bullet is in contact with the board.
s
Explanation / Answer
1) a) v = g t = 9.8 * 3.2
ball's initial velocity = 31.36 m/s
b) H = 1/2 g t2 = 1/2 * 9.8 * 3.22
height it reaches = 50.176 m
2) a) vf2 = v02 + 2 a d
2002 = 3002 + 2 a (0.08)
a = -3.125 * 105 m/s2
acceleration of the bullet as it passes through the board = 3.125 * 105 m/s2
b) t = change in speed / acceleration
= (200 - 300) / -3.125 * 105
= 3.2 * 10-4 s
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