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+ma)v
• D. (ma-R)v

Answer 1

The correct option is C

(R+ma)v

The engine has to do work against resistive force R as well as car is moving with acceleration a.
Force applied by the engine, $Force=(R+ma)$

$Power=Force\times velocity=(R+ma)v$