A ball is dropped from rest at point O (height unknown). After falling for some
ID: 2020229 • Letter: A
Question
A ball is dropped from rest at point O
(height unknown). After falling for some
time, it passes by a window of height 2.8 m
and it does so during time tAB = 0.44 s.
The acceleration of gravity is 9.8 m/s2 .
The ball accelerates all the way down; let
VA be its speed as it passes the window’s top
A and VB its speed as it passes the window’s
bottom B.
1- How much did the ball speed up as it passed the window; i.e., calculate Vdown = vBvA ? Answer in units of m/s.
2- Calculate the speed VA at which the ball passes the window’s top. Answer in units of m/s.
Explanation / Answer
Since it accelerates at the rate of 9.8 m/sec^2, in 0.44 sec it will increase in velocity 9.8*0.44= 4.312 m/sec To do 2 we solve the equation 2.8= Vo (0.44) +4.9 (0.44)^2 2.8= 0.44 Vo +0.94864 0.44 Vo= 1.85136 Vo= 4.208 m/sec
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