Q.

A sand dropper drops sand of mass m(t) on a conveyer belt at a rate proportional to the square root of speed (v) of the belt, i.e., dmdt∝v. If P is the power delivered to run the belt at constant speed then which of the following relationship is true          [2025]

1 P2∝v3  
2 P∝v  
3 P∝v  
4 P2∝v5  

Ans.

(4)

Power = F→·v→ and F=dpdt=Rate of change of linear momentum

              F=v·dmdt=Kv3/2, K is constant

Power (P)=(Kv)3/2·(v)=Kv5/2

So, P2∝v5