Question

8) A stone is dropped down a well. When it hits the bottom of the well, it is travelling at 20 m s-1. The mass of the stone is 20 g.
a. Calculate the kinetic energy of the stone as it hits the bottom of the well.
b. What is the gravitational potential energy of the stone at the top of the well?
c. Calculate the height of the well.

Answer 1

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First stone was per forming a free fall 

so time taken by it to coves the 

depth h=20m will be

t=g2h just by using h=21gt2

t=102×20=2 second

Second stone thrown 1 second later 

reaches simultaneously with first stone

so time taken will be t−1=2−1=1 second

the second stone will follow

h=vt1+21gt12

putting h=20m,9=10m/s2& t1=1sec

we get 

20=v+5×1⇒v=15mls 

Answer 2

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