# Numerical Problems Based on Class 11 Physics Linear Momentum and Force

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Momentum

Momentum of a body is the quantity of motion possessed by the body. It is equal to the product of mass and velocity of the body.

Momentum = Mass × velocity = mv

Momentum is a vector quantity because the velocity  is a vector and mass m is a scalar. Its direction is same as the direction of the velocity of the body. Its magnitude is given by

p = m v

SI unit of momentum = kg ms-1

CGS unit of momentum = g cm s-1.

The dimensional formula of momentum is [MLT-1].

Newton’s Second Law of Motion:

The rate of change of linear momentum of a body is directly proportional to the applied force and the change takes place in the direction of the applied force.

F = dp/dt

### Numerical Problems Based on Class 11 Physics Linear Momentum and Force

Q.1. A truck starts from rest and rolls down a hill with constant acceleration. It travels a distance of 400 m in 20 s. Calculate the acceleration and the force acting on it if its mass is 7 metric tonnes.

Q.2. A balloon has a mass of 5 g in air. The air escapes from the balloon at a uniform rate with a velocity of 5 cms-1. If the balloon shrinks completely in 2.5 s, find the average force acting on the balloon.

Q.3. A motor car running at the rate of 7 ms-1 can be stopped by applying brakes in 10 m. Show that total resistance to the motion, when brakes are on, is one fourth of the weight of the car.