A body of mass 4 kg is accelerated up by a constant force, travels a distance of 5 m in the first second and a distance of 2m in the third second. The force acting on the body is

Options

A. 6 N
B. 8 N
C. 2 N
D. 4 N

Answer

D

Explanation

The force is constant , i.e ., the acceleration is constant . The distance is decreasing with . Therefore it is retardation.
`1^(st)"second"u*1-(1//2)a*1=5m` …….. (i)
`3^(rd)"second"u*3-(1//2)*9-(u*2)a*4)=3`m.
`thereforeu*1-(1//2)a*5=3`.
(i) -(ii) gives `(1//2)a*4=-2rArra=-1m//s^(2)`.
`therefore` Constant force `=ma4xx1=4N`.
(This is a retarding force as a is negative).