A boy stands at the bottom of a 39.2 m tall building. He throws a ball upward which just reaches a window 19.6 m above the ground. What is the velocity of projection?

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Solution

Step 1, Given data
Total distance traveled h = 19.6 m
Final velocity v = 0
Acceleration due to gravity g = 9.8 m/ $s^{2}$
Step 2, Finding the velocity of projection
According to the equation of motion
$v^{2} = u^{2} + 2 a s$
Putting all the values
$0 = u^{2} - 2 \times 9.8 \times 19.6$
After solving
u = 19.6 m/s
Hence the velocity of projection is 19.6 m/s

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