Why is is easier to push a heavy load on wheels with a short lever

[voyager221]

Why is it easier to push a load on a wooden crate on wheels when you are nearer the load and the lever is shorter and at a sharp angle compared to pushing a load with the lever lengthened and at a more relaxed angle with your body further away?

 

[256bits]

What is a 'sharp' angle and a 'more relaxed' angle?

 

[voyager221]

Sorry to confuse the angle isn't that important.

Imagine a small wooden crate on wheels with a load on it and there is a lever attached to the crate which you hold to push the crate along the ground.

If the lever is stretched out and lowered so that you are further from the crate it is apparently harder to push than if the lever is made shorter and raised so that you are much nearer the crate.

Why is this?

 

[DaveC426913]

Torque - specifically the length of the lever arm.

http://en.wikipedia.org/wiki/Torque

In the case of the crate, torque works against you, because your goal is not to turn the create but to keep it moving in a straight line. A longer lever arm means you are farther from the centre of mass of the crate.