Question

A ball is going vertically upwards with a velocity of 20 ms-1, When it is 60m above the ground, a stone is released from it. The time taken by the stone to reach the ground is(g = 10ms 2s 4s 8s 6S​

Answer 1

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Time to reach maximum height can be obtained from v=u+at

0=20+(−10)t

t=2s

s=ut+0.5at²

=20(2)+0.5(−10)(2)² =20m

Thus, total distance for maximum height is 45 m

s=ut+0.5at²

45=0+0.5(10)(t')²

t′ =3s

Total time= 3+2= 5s

Answer 2

Answer:

Step-by-step explanation:

Let the height from which the stone is released be h.

The upward velocity u of the stone when dropped from height h = 10 m/s.

The further height d to which the stone will rise further can be found from the relation;

v² - u² = 2 g d

0² - 10² = - 2× 10×d; ==> -20 d = -100, or d = 5 m.

Time taken to go up 5m can be found using

v = u + a t. At the highest point v=0 m/s, u = 10 m/s, t =1 s.

The stone starts to fall from a height (h +5)m, with an initial velocity zero, and an acceleration +10 m/s², and in time t =11 s -1s = 10s reaches the ground. Using the relation

s = u t + ½ a t², we can find s.Substituting for u, a and we get s, we get

s = 0×10 + ½ ×10×10² = 500m

s = h + 5 = 500 m; ==> h = 495 m.

The height of the balloon when the stone was dropped from it = 495 m.