A truck and a car are moving with the same K.E. on a straight road. Their engines are simultaneously switched off. Which one will stop at a lesser distance ?

Options

A. `d_(1)=d_(2)`
B. `d_(1)gtd_(2)`
C. `d_(1)ltd_(2)`
D. `d_(1)=2d_(2)`

Answer

C

Explanation

For a freely falling body, `v^(2)=u^(2)+2gs` (without air resistance)
`therefore v^(2)=0+2 xx 10 xx 20=400`
`v=20m//s`. It should acquire this velocity. But it acquires a velocity of 10m/s.
This is because of the air resistance opposing the motion of the body.
Loss in K.E. =Work done by the air resistance
`therefore 1/2 m[v^(2)^(2)-v_(1)^(2)] =W`
`therefore W=1/2 xx 10 xx (400-100)`
` W=1500J `