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. $(ma-R)V$
• B. $(R+ma)V$
• C. $maV$
• D. $RV$

Answer 1

The correct option is B $(R+ma)V$

Formula Used: $P=F.v$
Given, mass of car $=mkg$
Acceleration $=a$
Resistive force $=R$
Velocity of car $=V$
As the power is given by,
$P=F.v$
Force is required to oppose the resistive force $R$and also to accelerate the body of mass with acceleration 𝑎.
$F-R=ma$ $F=R+ma$ $P=FV=(R+ma)V$
$\text{power}\left(P\right)=(R+ma)V$

Final Answer: (c)