The velocity of a body of mass 20 kg decreases from `20m//s` to `5m//s` in a distance of 100 m. Force on the body is:

Options

A. `-27.5N`
B. `-47.5N`
C. `-37.5N`
D. `-67.5N`

Answer

C

Explanation

Here `m=20kg ,u=20m//s, v=5m//s`
s=100m
Using `v^2-u^2=2as` or `a=(v^2-u^2)/(2s)`
Force F=mass (m) `times` acceleration (a)
`F=m times ((v^2-u^2)/(2s))`
Substituting the values , we get
`F=20 times [((5)^2 -(20)^2)/(2 times 100)]=20[ (25-400)/200]`
`F=20 times [(-375)/200]=-37.5N`