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

We are standing in a bus moving with constant velocity. When brakes are applied to the bus,we are thrown in the forward direction. Why?

$A$ girl jumps down from a moving bus,along the direction of motion of the bus,tilting slightly forward. She falls on $(a)$ a sheet of ice $(b)$ a patch of glue. Which of the following statements is correct regarding her fall?

The displacement versus time graph for a body moving in a straight line is shown in the figure. Which of the following regions represents the motion when no force is acting on the body?

Physical independence of force is a consequence of

Due to which property of an object does it resist any attempt to change its state of motion?