Q.19:- A trolley of mass 300 kg carrying a sandbag of 25 kg is moving uniformly with a speed of 27 km/h on a frictionless track. After a while, sand starts leaking out of a hole on the floor of the trolley at the rate of 0.05 kg s–1. What is the speed of the trolley after the entire sand bag is empty?
As the trolley carrying the sand bag is moving uniformly, therefore, external force on the system = 0.
When the sand leaks out, it does not lead to the application of any external force on the trolley. Hence, the speed of the trolley shall not change.