Question

A vehicle is moving on a straight horizontal road at a constant velocity of $10m{s}^{-1}$. The engine needs to spend $4kJ$ of energy per second. The force on the vehicle is

• A. $0.2kN$
• B. $0.4kN$
• C. $0.6kN$
• D. $1N$

Answer 1

The correct option is B

$0.4kN$

Step 1: Given data and assumptions

The velocity of a moving vehicle is $v=10m{s}^{-1}$

The power of the engine is $P=4kJ/s$

Let the force on the vehicle be $F$

Step 2: Finding the force on the vehicle

We know that,

$$\begin{gathered} Power=Force\times velocity \\ \mathrm{Therefore}, \\ Force=\frac{Power}{velocity} \\ F=\frac{4}{10}kN \\ F=0.4kN \end{gathered}$$

Thus, the force on the vehicle is $0.4kN$.

Hence, option (b) is correct.