Question

An open carriage in a goods train is moving with a uniform
velocity of 10 m/s. If the rain adds water with zero velocity at the rate of 5
kg/s, then the additional force required by the engine to maintain the same
velocity of the train is

• A. 0.5 N
• B. 20 N
• C. 50 N
• D. zero

Answer 1

The correct option is D zero

The correct option is (c)

As we know:

$\begin{array}{c}F=V_{\text{relative}}\frac{dm}{dt}\\ \text{Here ;}\frac{dm}{dt}=5{kg}_{\text{s}}\text{(Given)}\end{array}$

So,

$F=10\times 5$

$50N$

For constant speed i.e. $a=0$