Question #8a35a

1 Answer
Jun 25, 2015

For a simple machine mechanical advantage (MA) = loadeffort

Efficiency =Mechanical advantageVelocity ratio×100

Explanation:

Mechanical advantage = LoadEffort

So if we look at a simple 1 pulley system:

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The effort = the load so MA=1. In this case there is no mechanical advantage gained from such a system.

You can increase the number of pulleys to increase the MA.

Gears work like this.

Velocity Ratio (VR) = distance moved by effortdistance moved by load.

Again, in the 1 pulley system VR=1.

Work done = Force x distance moved in the direction of that force.

If we divide MA by VR we get:

MAVR=load×distance moved by loadeffort×distance moved by effort

So this ratio is a measure of the work done on the load compared with the work done by the effort.

In an ideal world the work put in by the effort would equal the work done on the load. However, we don't live in an ideal world.

There are energy losses due to friction and heat etc which means that machines are rarely 100% efficient.

We usually express this as a percentage:

Efficiency=MA/VR×100