Question

11. A ball is thrown straight upwards into the air with an initial velocity of 20 m s-1. How long will it take the ball to reach a height of 15 m? How fast will it then be going? (Take g = 10m s-2)
(Ans. 1 s 10 m s-)​

Answer 1

Explanation:

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

0=20+(−10)t

t=2s

s=ut+0.5at

2

=20(2)+0.5(−10)(2)

2

=20m

Thus, total distance for maximum height is 45 m

s=ut+0.5at

2

45=0+0.5(10)(t

′

)

2

t

′

=3s

Total time= 3+2= 5s

not the same answer

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