Answer :

(i) The value of acceleration due to gravity *g* will be taken as negative as the ball is going upwards.

Given,

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

Final velocity of ball, *v* = 0 (As the ball stops at top)

Acceleration due to gravity, g = - 9.8 m/s^{2}

Height, h =?

We know that,

v^{2} = u^{2} + 2gh

(0)^{2} = (49)^{2} + 2 × (-9.8) × h

0 = 2401 – 19.6 h

19.6 h = 2401

h =

= 122.5 m

(ii) Now, we will calculate the time taken by the ball to reach at the highest point:

Given,

Final velocity, v = 0 (As the ball stops at top)

Initial velocity, u = 49 m/s

Acceleration due to gravity, g = - 9.8 m/s^{2}

Time taken, *t* =?

0 = 49 + (-9.8) × *t*

0 = 49 – 9.8 *t*

9.8 t = 49

t =

t = 5 s

The ball will take equal time to return to the surface of earth.

Therefore, Total time = 5 + 5

= 10 seconds

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