Question

A ball is moving with a initial velocity of 20 m/s and final velocity of
80 m/s, find the time travel by the ball. (Take g= 10 m/s2).
OR
A ball is vertically thrown upwards with a velocity of 40 m/s. Calculate
the maximum height reached to the ball. (Take g = 10 m/s2).​

Answer 1

Explanation:

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/s

2

holds true (maximum height reached is small compared to the radius of earth)

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

v

2

−u

2

=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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