Final answer:
Applying oil to a machine reduces friction and increases its velocity ratio. The efficiency of a pulley is affected by factors such as friction, the number of pulleys, and the angle of the rope or belt.
Step-by-step explanation:
Applying oil to a machine does affect its velocity ratio.
The velocity ratio of a machine is the ratio of output velocity to input velocity. By applying oil, the machine's moving parts become lubricated, reducing friction between them.
This reduction in friction allows the machine to operate more smoothly and efficiently, resulting in a higher velocity ratio.
The factors that affect the efficiency of a pulley include friction, the number of pulleys in the system, and the angle at which the rope or belt is wrapped around the pulley.
Friction can decrease the efficiency of a pulley system by causing energy losses.
Increasing the number of pulleys can increase the mechanical advantage of the system, but can also introduce more friction.
Wrapping the rope or belt at a steeper angle can also increase the efficiency by reducing the force required to lift a load.