Question

Please help me with this question
A body is dropped from a height h from the state of rest. It covers a distance of 9h/25 in the last second. What is the height from which the body falls?(in meters)
A. 12.5
B. 1.25
C. 125
D. Zero
Someone give me a proper detailed answer pleaseeeeeee

Answer 1

Answer:

C. 125 m

Explanation:

Let total time taken be "T" seconds

Use equation of motion

• S = ut + 0.5at²

For total fall

h = (0 × T) + (0.5gT²)

h = 0.5gT² .......(1)

For the time t = T - 1 seconds

h - 9h/25 = (0 × T) + 0.5g(T - 1)²

16h/25 = 0.5g(T - 1)² .......(2)

Divide equations (1) and (2)

h / (16h/25) = 0.5gT² / [0.5g(T - 1)²]

25/16 = [T / (T - 1)]²

5/4 = T / (T - 1)

5T - 5 = 4T

T = 5 seconds

Substitute T = 5 s in equation (1)

h = 0.5gT²

= 0.5 × 10 m/s² × (5 s)²

= 125 m