Question

a ball is thrown velocity downwards with velocity u from a height h find the striking time of the ball ​

Answer 1

Explanation:

Initial energy E

i

=PE+KE=mgh+

2

1

mv

2

Energy when it reaches the ground: E=

2

1

mv

′2

since PE is zero.

Given, E=

2

1

E

i

Since it rises to the same height E

f

=mgh+0 is the final energy

⇒

2

1

(mgh+

2

1

mv

2

)=E

f

=mgh+0

v

2

=2gh=2×10×20=20

2

⇒v=20m/s