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ClassAct SRS enabled. In this presentation you will : identify the use of levers in hydraulic applications. In this presentation you will see first, second and third class levers. You will also see hydraulics applications where levers are used. Next &gt;. Mechanical Levers.

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ClassAct SRS enabled.

In this presentation you will:

• identify the use of levers in hydraulic applications

You will also see hydraulics applications where levers are used.

Next >

Mechanical Levers

Levers are simple mechanisms used to apply mechanical advantage.

For example, by using a stiff branch resting on a log, early man was able to lift heavy rocks.

A lever can be a long bar that rests on a pivot point (fulcrum). An effort is applied to move the load.

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Lever Classification

First Class

There are three classes of levers. They differ in the placement of the fulcrum, effort and load along the lever.

The three types are:

• First class lever

Second Class

• Second class lever
• Third class lever

Third Class

Sometimes these are also referred to as first order, second order and third order levers.

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Question

1

The lever shown is a:

A) first class lever

B) second class lever

C) third class lever

Effort

Fulcrum

First Class Lever

First class levers are the most common type of lever. The fulcrum is between the effort and the load.

A mechanical advantage of force is achieved if the distance between the effort and fulcrum is longer than that between the load and fulcrum.

The lever will balance if the load and effort are equal, and they are also both the same distance from the fulcrum. The system is in equilibrium.

A seesaw is an example of a first class lever. Other examples are a claw hammer, crowbar, scissors and weigh scales.

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small distance

Small effort,

large distance

Second Class Levers

The load is between the effort and the fulcrum. Second class levers provide mechanical advantage of force, as the effort is always further away from the fulcrum than the load.

This allows a large load to be lifted a small distance by a smaller effort moving a larger distance.

A wheelbarrow is an example of a second class lever. Other examples include bottle openers, foot pumps and nut crackers.

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Question

2

In a second class lever, where should the effort be placed?

A) On the opposite side of the fulcrum to the load

B) On the same side of the fulcrum as the load, but further away from the fulcrum

C) Between the load and the fulcrum

D) On the opposite side of the fulcrum but very close to it

Effort

Fulcrum

Third Class Levers

The effort is applied between the load and the fulcrum. The effort is closer to the fulcrum than the load.

This means the effort force needs to be larger than the load, but with the advantage that the load moves a greater distance than that moved by the effort.

An engine hoist is an example of a third class lever. Other examples are tweezers and fishing rods.

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Question

3

Which of the following is an example of a third class lever?

A) Wheel barrow

B) Scissors

C) Fishing rod

D) See-saw

Hydraulic Systems Using Mechanical Levers

Many construction machines make use of the hydraulic lever principle, whether they are excavating, lifting, grading, or drilling machines.

First class lever

Third class lever

An excavator uses a hydraulic cylinder to push up the boom, but the boom is itself a type of lever. A short movement of the cylinder makes the end of the boom move much further.

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Question

4

On an excavator, what part of the lever mechanism does the cylinder represent?

B) Effort

C) Fulcrum

D) Lever

Cylinder

Summary

You should now be aware of:

• Different classes of lever
• Examples of levers in hydraulic systems

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