Question

A stone is dropped from the top of the tree covers 6m height in last 0.2s of fall. find height of the tree

Answer 1

Explanation:

Let it will take T time to cover the whole length

so we can say

H = \frac{1}{2}gT^2H=

2

1

gT

2

now in last 0.2 s it will cover 6 m

H - 6 = \frac{1}{2}g(T - 0.2)^2H−6=

2

1

g(T−0.2)

2

now by above two equations

\frac{1}{2}gT^2 - 6 = \frac{1}{2}g(T-2)^2

2

1

gT

2

−6=

2

1

g(T−2)

2

\frac{1}{2}g(2T - 2)(2) = 6

2

1

g(2T−2)(2)=6

T = 1.3 sT=1.3s

now the height of the tree is

H = \frac{1}{2}*10*1.3^2H=

2

1

∗10∗1.3

2

H = 8.45 mH=8.45m