Why is a large initial force required to accelerate a heavy object?

$A$ 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 $0.05 \; kg \cdot s^{-1}$. What is the speed (in $km/h$) of the trolley after the entire sandbag is empty?

$A$ body of mass $2 \, kg$ is sliding with a constant velocity of $4 \, m/s$ on a frictionless horizontal table. The force required to keep the body moving with the same velocity is .......... $N$.

$A$ rider on horseback falls when the horse starts running all of a sudden because:

When a train stops suddenly,passengers in the running train feel an instant jerk in the forward direction because

Explain the difference between mass and weight.