I dont understand why speed will remain constant when sand is removed???Question 10:-
When sand is added, the mass increases. Therefore, its speed decreases since energy is nor created nor destroyed so k.e=0.5mv^2 has to be constant
When it is removed, some k.e is lost when it is dropeed out. Therefore, k.e decreases when its mass is less. Its speed will remain constant because it needs a force to give it a higher speed forward i.e Answer is B.