Question

A ball is thrown vertically upward with the velocity 20 m/s. Calculate 1) how high it goes ii) the time taken to reach the maximum height (taking acceleration due to gravity g -9.8 m/s) ​

Answer 1

Given Initial velocity of ball, u=49 m/s

Let the maximum height reached and time taken to reach that height be H and t respectively.

Assumption: g=9.8 m/s2 holds true (maximum height reached is small compared to the radius of earth)

Velocity of the ball at maximum height is zero, v=0

v2−u2=2aH                          

0−(49)2=2×(−9.8)×H         

⟹H=122.5 m               

v=u+at

0=49−9.8t            

⟹t=5 s

∴ Total time taken by ball to return to the surface, T=2t=10 s 

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