Because too much friction can damage the simple machines that make up the compound machine.
less wear
If I'm not mistaken, there is no machine that can reduce friction. The machine is intended to change the distance the input force is applied over or to multiply the output force. The moving parts of the machine will always increase friction. In order to reduce the extra friction (but not completely remove it), one would use a lubricant or reduce the roughness between two surfaces. Hope it helps.
You can reduce friction by using lubrication, like grease for bearing, sewing machine oil etc.
To reduce the friction
A lubricant such as oil and ball bearings are just (2) methods of reducing friction.
Oil it
less wear
If I'm not mistaken, there is no machine that can reduce friction. The machine is intended to change the distance the input force is applied over or to multiply the output force. The moving parts of the machine will always increase friction. In order to reduce the extra friction (but not completely remove it), one would use a lubricant or reduce the roughness between two surfaces. Hope it helps.
You can reduce friction by using lubrication, like grease for bearing, sewing machine oil etc.
To reduce the friction
I think it would a lubricant not a part...
A lubricant such as oil and ball bearings are just (2) methods of reducing friction.
Friction force oppose motion between two bodies that are in contact. This force is important in machines and pulley systems in that it enables the gears to have grip and there is no unnecessary sliding.
Because some energy is expended in overcoming the friction and not applied to performing the task which the machine is meant to do.
Friction creates heat. Heat could melt machine parts if it becomes too high. That's why many machines use lubricants while they're drilling or shaping metal.
No, sand does not reduce friction but increase friction.
When a machine is running at 100 % efficiency there is no loss of energy anywhere. That means the machine is running silently and if turned off will continue to run without stopping. In the real world there is sound and there is friction. Both sound and friction are examples of less than perfect efficiency