Physics [1 Mark Question Answer]

When the effort moves by a distance d downwards, the load moves by the same distance upwards. So, height to which the load moves is 8 m.

The load rises upwards with the same distance x .

The velocity ratio of a single fixed pulley is 1.

The ideal mechanical advantage of a single fixed pulley is 1.
It cannot be used as force multiplier.

A pulley which has its axis of rotation fixed in position is called a fixed pulley.
A single fixed pulley is used in lifting a small load like a water bucket from the well.

Change the direction of force applied: single fixed pulley.

Multiply speed: gear system or class III lever.

To multiply force: a jack is used to lift a car.

The efficiency depends upon the mass of lower block; therefore efficiency is reduced due to the weight of the lower block of pulleys.

This is because mechanical advantage is equal to the total number of pulleys in both the blocks.

This is because of some effort is wasted in overcoming the friction between the strings and the grooves of the pulley.

The load is raised to a height of x/2 .

The velocity ratio of a single movable pulley is always 2 .

When efficiency reduces, its mechanical advantage reduces and velocity ratio remains the same. So, when efficiency becomes 50%, M.A. = 0.9 and V.R. = 1.8

Length of the lever is same as the effort arm. Also, effort arm is more than load arm. So, this is a class II lever.

In actual machine there is always some loss of energy due to friction and weight of moving parts,
thus the output energy is always less than the input energy.

It is the ratio of the useful work done by the machine to the work put into the machine by the
effort.

For an ideal machine mechanical advantage is numerically equal to the velocity ratio.

The ratio of the velocity of effort to the velocity of the load is called the velocity ratio of machine. It has no unit

The ratio of the load to the effort is called mechanical advantage of the machine. It has no unit.

The purpose of jack is to make the effort less than the load so that it works as a force multiplier

A fishing rod lever is Class III .

A wheel barrow lever is Class II .

A catapult lever is Class I .

A door lever is Class II .

To obtain gain in speed: when a pair of scissors is used to cut the cloth, its blades move longer on cloth while its handles move a little.

With levers of class III, we do not get gain in force, but we get gain in speed, that is a longer displacement of load is obtained by a smaller displacement of effort.

To change the point of application of force: the wheel of a cycle is rotated with the help of a chain by applying the force on the pedal.

In these types of levers, the effort is in between the fulcrum F and the load L and so the effort arm is always smaller than the load arm. Therefore M.A. < 1.

To multiply force: a jack is used to lift a car.

It is second-class of the lever

In these types of levers, the load L is in between the effort E and the fulcrum F. So, the effort arm is thus always longer than the load arm. Therefore M.A>1.

Class II lever always has a mechanical advantage more than one.
Example: a nutcracker.
To increase its mechanical advantage we can increase the length of effort arm.

Less than one: a pair of scissors whose blades are longer than its handles .

More than one: shears used for cutting the thin metal sheets .

A lever is a rigid, straight or bent bar which is capable of turning about a fixed axis .

A machine acts a speed multiplier when the effort arm is shorter than the load arm. The
mechanical advantage of such machines is less than 1.

A machine acts as a force multiplier when the effort arm is longer than the load arm. The
mechanical advantage of such machines is greater than 1.