Tag: motion in application

A doorknob functions as a wheel and axle, where turning the larger wheel (knob) creates a mechanical advantage to turn the smaller axle (latch mechanism).

Velocity ratio of simple machine is the ratio of distance traveled by the effort to the distance traveled by the load in the machine. As velocity ratio or ideal mechanical advantage is a simple ratio of two distances.Hence always remains constant.
Option A is correct.
 

C. A pulley is the example of simple machine

A lever, screw and wheel are example of simple machine. 

A force which is applied at one point on the lever in order to move an object is called $effort$ force and hence is the part of lever which we are trying to move. 

A flagpole uses a pulley at the top to allow a rope to change the direction of the force, making it easier to raise the flag.

D. Wedge is used to split a log. An axe or knife blade is a wedge.

D. Screw is simple machine which is used to hold to objects together

Move the fulcrum close to the load to reduce the amount of effort needed to lift something using a first class lever.If, we move the fulcrum towards the effort end, the length of effort arm will reduce and that of load arm will increase, resulting in a lower mechanical advantage and necessitating more effort to do the same amount of work.As a result, the mechanical advantage is more (and less effort would be required).