Question

A ball is dropped from certain height such that the
distance travelled in last second is equal to the
distance travelled in first three second. Find its
height.
(1) 80 m
(2) 180 m
(3) 145 m
(4) 125 m
​

Answer 1

Answer:

145

Explanation:

Answer 2

Answer:

The Answer is 125m

Explanation:

This can be explained easily by Galileo's law of odd numbers. It's a simple law which states that a body when dropped vertically from a height will cover distances in the ratio of 1:3:5:7.... in equal intervals of time.

Therefore at any given interval of time, the body must cover (2n-1).x meters in the nth interval, where n can take all values from 1 to infinity and x is the distance covered in the 1st second where n=1.

As per the given conditions if the body travelled for k seconds then,

(2k-1).x = x + 3x + 5x = 9x.

Solving, we get k=5. ie; The body travelled for a total of 5 seconds. Then using kinematic equation , s=u.t-1/2.a.(t^2) , (u=0,a=g(=10)) we obtain s=125m.