Q18 of 61 Page 318

A boy drops a stone from a cliff which reaches on the ground in B seconds. Calculate

(i) height of cliff


(ii) final velocity of the stone

Let H be the height of the cliff.


Now, ball is initially at rest


So, u = initial velocity = 0


a = acceleration = g


v = final velocity


t = B seconds


(i) From the equations of motion, we know that,





(ii) Now, we also know that,


v = u + at


v = 0 + gB


v = gB


More from this chapter

All 61 →
16

State Newton’s law of gravitation. Explain it.

 17

Derive an expression for the acceleration due to gravity on the surface of the earth. State the factors on which g depends. How does it vary with depth? Where is it maximum on the surface of the earth?

 19

A stone thrown vertically upwards takes 3 seconds to attain maximum height, calculate

(i) initial velocity of stone


(ii) maximum height attained by the stone

 20

Prove that if a body is thrown vertically upwards, then the time of ascent is equal to the time of descent.