Test: Newton's First Law Of Motion - Class 9

When the bus is not moving the passengers are in the state of rest and they have inertia of rest. When the bus starts moving suddenly, the lower part of the body of passengers, which is in contact with the bus, come in motion, but upper part of their body tends to be in the state of rest and the passengers fall backward.

Inertia of stone is greater than the inertia of football because mass of stone is higher than the mass of football even both are of same size.

Force - force of friction = mass × acceleration
250 - f = 30 × 4
f = 250 - 120
= 130N

When a hanging carpet is beaten with a stick, the dust particles are removed from it because the carpet on beating suddenly moves forward and the dust particles due to inertia of rest continue to remain at rest. Hence the dust particles fall down and the carpet gets cleaned.

If no force is applied to a moving object, it should remain in motion as per the first law of motion. But, it is stopped due to friction.