Isaac Newton’s Laws of Motion describe how forces change the motion of an object, how the force of gravity gives weight to all masses, how forces cause acceleration and how forces work in collisions.

Newton's Second Law is concerned with **unbalanced** forces. Unbalanced forces produce acceleration. The greater the unbalanced force the greater the acceleration. This law is usually written as an equation:

Where unbalanced force is measured in Newtons ( ), mass in kilograms ( ) and acceleration in metres per second per second ( )

Remember that it is an **unbalanced** force that is required here.

- Question
A car's engine force is 3000 and its mass is 1500 .

A frictional force of 500 acts over a distance of 20 .

Calculate the acceleration of the car.

Unbalanced force:

The acceleration of the car is 1.67 .

- Question
Calculate the work done in moving the car against friction.

Work done against friction moving car = 1000 .