Question

A conveyor belt is moving horizontally with a uniform velocity of 2 m/s. Material is dropped at one end at the rate of 5 kg /s and discharge at the other end. Neglecting friction, the force required to move the belt is [in Newtons]

• A. 10
• B. 15
• C. 20
• D. 40

Answer 1

The correct option is A 10

The net force should be defined by Newton's Second Law;

$F=\frac{d\left(P\right)}{dt}=\frac{d\left(mv\right)}{dt}=m\frac{dv}{dt}+v\frac{dm}{dt}$

here, speed changes but mass varies;

$\frac{dm}{dt}=5kg/s$ and $v=2m/s$

$F_{net}=2\times 5+0=10N$