Question

A stone is dropped from the top of a cliff It is seen to hit the ground below after 4.2s How high is the cliff? ​

Answer 1

AnswEr

GivEn that, a stone is dropped from the top of a cliff is seem to hit the ground below after 4.2sec.

We've to find the height of the cliff.

So,

We need to use the concept of Time period.

Time Period is the time taken to traverse the path by the projectiler.

We know that in this case the object starts from rest will take time T in falling height h given by,

↬ T = √2h/g

Substituting the values :

↬ 4.2 = √2h/9.8

Squaring both the sides :

↬ (4.2)² = 2 × h/9.8

↬ 4.2 × 4.2 = 0.20 × h

↬ 17.64 = 0.20h

↬ h = 17.64/0.20

↬ h = 88.2m

∴ Height of the cliff is 88.2 m(approx.)