Question

A car of mass ‘m’ is driven with acceleration ‘a’ along a straight level road against a constant external resistive force ‘R’. When the velocity of the car is ‘v’, the rate at which the engine of the car is doing work will be

• A. Rv
• B. mav
• C. $( R + m a ) v$
• D. $( m a - R ) v$

Answer 1

Answer: (C)

$( R + m a ) v$

Answer 2

The engine has to do work against resistive force R as well as car is moving with acceleration a.

Power = Force × velocity = (R+ma)v.