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 ?

A man weighing 70 kg, riding a motorbike weighing 230 kg at 54 km hr^(

1.	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 ?
Answer» `1.5N` `2.5N` `3.5` `4.5N` Solution :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.

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