Question

what are the M.A. & V.R. of different classes of levers?

Answer 1

Hey there!

What is a Lever ?
A lever is a rigid bar which is capable of turning around a fixed axis.

Levers are classified as -:

1) Class I lever -: Fulcrum is in between load & effort
2) Class II lever -: Load is in between the fulcrum & effort
3) Class III lever -: Effort is in between the load & fulcrum

The Mechanical Advantage and Velocity Ratio of Class I lever can be greater than one, equal to one, or less than one. Hence it can be uses as a force multiplier, speed gainer and to change the direction of effort at a convenient point.

The Mechanical Advantage and Velocity Ratio of Class II lever is always greater than one. Hence it can be used as a force multiplier.

The Mechanical Advantage and Velocity Ratio of Class III lever is always less than one. Hence it can be used as a speed gainer.

;-)

Answer 2

You need to know how to calculate the mechanical advantageobtained by using levers, the velocity ratio in levers and pulley systems, and gear ratio and output speed when using gears.

A lever is the simplest kind of mechanism. There are three different types of lever. Common examples of each type are the crowbar, the wheelbarrow and the pair of tweezers.

All levers are one of three types, usually called classes. The class of a lever depends on the relative position of the load, effort and fulcrum:

The load is the object you are trying to move.The effort is the force applied to move the load.The fulcrum (or pivot) is the point where the load is pivoted.

Class 1 levers

A class 1 lever has the load and the effort on opposite sides of the fulcrum, like a seesaw. Examples of a class-one lever are a pair of pliers and a crowbar.

For example, it would take a force of 500N to lift the load in the animation below. But using a lever - a rod with the fulcrum placed closer to the load than the point of effort - it only requires a force of 100N. Press play to see a demonstration.



Class 2 levers



A class 2 lever has the load and the effort on the same side of the fulcrum, with the load nearer the fulcrum. Examples of a class-two lever are a pair of nutcrackers or a wheelbarrow.

In the diagram, the wheel or fulcrum on the wheelbarrow is helping to share the weight of the load. This means that it takes less effort to move a load in a wheelbarrow than to carry it.

Mechanical advantage and velocity ratio

Class 1 and class 2 levers both provide mechanical advantage. This means that they allow you to move a large output load with a small effort. Load and effort are forces and are measured in Newtons (N). Mechanical advantage is calculated as follows:

Mechanical advantage = load ÷ effort

In the example above, where the load=500N and the effort=100N, the mechanical advantage would be:

500N ÷ 100N = 5

Velocity ratio

The mechanical advantage gained with class-one levers and class-two levers makes it seem like you are getting something for nothing: moving a large load with a small effort. The catch is that to make the effort smaller, you have to move a greater distance. In the first diagram the trade-off is that you need to push the lever down further to move the load up a smaller distance. This trade-off is calculated by the velocity ratio:

Velocity ratio = distance moved by effort ÷ distance moved by load