‘Weight’ is the force exerted by gravity on a body. To lift something up, you must exert a greater upward force to overcome the downward force. The amount of ‘work’ you have to do to achieve this depends on the weight of the object and the distance you have to move it. Some things are too heavy for you to lift alone, and you need help — another person or a machine perhaps. Machines make our lives easier by doing work or helping us to do work.

A lever is a simple machine which can help you lift things, like the lid of a tin. Ramps can also overcome force — it is easier to roll an object than to lift it.

The way levers work is by multiplying the effort exerted by the user. Specifically, to lift and balance an object, the effort force the user applies multiplied by its distance to the fulcrum must equal the load force multiplied by its distance to the fulcrum. Consequently, the greater the distance between the effort force and the fulcrum, the heavier a load can be lifted with the same effort force.

A wedge and an inclined plane are similar. An inclined plane is also known as a ramp. A ramp is a flat surface with one end higher than the other. Gravity makes it easier to move a heavy load up and down an inclined plane than to move that same load straight up or down without the help of a simple machine. A wedge is two inclined planes placed back to back and put into action.