Video: The inclined plane

Can you lift this 50kg box 1 meter high?

A 50 kg mass undergoes an equal downward force : its weight

The magnitude of this force is about 500 Newtons.

To lift it, the resistance force must be counteracted by exerting an opposite and equal magnitude effort force.

If the box is too heavy, then muscular force isn’t enough to lift it.

The inclined plane is a simple machine used to change the direction and the magnitude of the resisting force.

The force of gravity can be resolved into two components:

• one directed perpendicular to the inclined surface…

• and the other directed parallel to the inclined surface

The normal force balances the perpendicular force.

The net force is simply the parallel force component … and the force or friction which prevents the box from sliding.

Let’s get rid of friction!

To move the box along the inclined surface, an effort force has to be exerted to counteract this new resistance force.

The Mechanical Advantage of the inclined surface relies on the fact that the magnitude of the resistance force is less than the weight.

For this surface inclined at an angle of 30 degrees, the mechanical advantage is equal to 2.

 The gentler the slope the greater the mechanical advantage.

However, what has just been gained in force has been lost in the distance to cover.

The energy required to move the box is the result of the force multiplied by the distance.

Due to conservation of energy, effort force must be increased if the distance is decreased.

The work done lifting the box remains the same.

Where energy is concerned, remember that nothing is lost, nothing is created, everything is transformed.