In free fall, a body of mass 1kg drops from a height of 125m from rest in 5s. How long will it take another body of mass 2kg to fall from rest from the same height?

Physics Jamb, Waec, Neco Past Questions & Answers on Speed, Velocity and Acceleration

QUESTIONS 46: In free fall, a body of mass 1kg drops from a height of 125m from rest in 5s. How long will it take another body of mass 2kg to fall from rest from the same height? 

[g=10ms–2] A. 5s B. 10s C. 12s D. 15s 

JAMB 1998 

Ans:5s

Solutions

First Body

M¹ = 1kg

H¹ = 125m

t¹ = 5s

u = 0m/s

Second Body

M² = 2kg

h² = 125m

t² = ?

u = 0m/s

g = 10m/s²

Solving for the second body 

h = ut + ½gt²

125 = 0 x t + ½(10)t²

125 = 0 + 5t²

125 = 5t²

t² = 125/5

t² = 25

t = √25

t = 5s

Alternatively 

In the absence of external resistance all objects falling under gravity will hit the ground at the same time no minding the amount of mass or weight they possess.

Therefore since it took the first Body 5s to fall, the same time is app

licable to the second body.