A man weighing 70 kg, riding a motorbike weighing 230 kg at `54 km hr^(-I)`, accelerates at `Ims^(-2)` for 10 s when suddenly a child rushes into the road. The rider manages to apply brakes screeching to bring his vehicle to a halt in 3 s, just in time to save the child. What should have been the average retarding force on the vehicle ?

Options

A. `1.5N`
B. `2.5N`
C. `3.5`
D. `4.5N`

Answer

(none)

Explanation

Here `u = 54xx =(5)/(18)= 15 m//s`
:. velocity attained in 10 s is given by
`upsilon = u + at impliesupsilon = 15 + 1 xx 10 = 25 m//s`
For retarded motion
`u. = 25 m//s, upsilon = 0,t = 3s`
`:.upsilon = u. + a. timplies 0= 25+ a. xx 3`
`a. =(-25)/(3)m//s^(2)`
:.Retarding force F = (M+ m) retardation
`=300xx(25)/(3) =2.5xx10^(3)N`
So correct choice is (E) as none of the choices given in question is correct.