LEVERS - Mechanical advantage - Bolt cutters can deliver a staggering force of 20 kilonewtons, that is the equivalent of around 2,040 kilograms. It is even more impressive when you think that this is done by the person only applying a force on the handles equivalent to 25 kilograms or 250 kilonewtons - By using a lever Jonathon can lift a load of 3000N using an effort of just 300N. We say that the lever has a mechanical advantage. Bolt cutters can deliver a staggering force of 20 kilonewtons, that is the equivalent of around 2,040 kilograms. It is even more impressive when you think that this is done by the person only applying a force on the handles equivalent to 25 kilograms or 250 kilonewtons. Second order levers - A lever that has the load between the fulcrum and the effort is known as a second order lever. Once again, the further away the effort is from the fulcrum and the load the greater the mechanical advantage of the lever. Third order levers - A third order lever is one which has the effort between the fulcrum and the load. Such levers do not have good mechanical advantage. In fact they have mechanical disadvantage. The effort is closer to the fulcrum than the load. The effort is always greater than the load. However, one advantage of such levers is that the distance moved by the load is greater than the distance moved by the effort. Cranes such as the one on the left are examples of third order levers. As you can see the effort is between the load, at the top, and the fulcrum. The advantage of this lever system is that the load moves through a greater distance than the effort. This is desirable when the crane needs to lift loads high above the ground. Tweezers are another example of a third order lever.

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Levers

Mechanical advantage.

Bolt cutters can deliver a staggering force of 20 kilonewtons, that is the equivalent of around 2,040 kilograms. It is even more impressive when you think that this is done by the person only applying a force on the handles equivalent to 25 kilograms or 250 kilonewtons.    

dynamicscience.com.au

 

By using a lever Jonathon can lift a load of 3000N using an effort of just 300N. We say that the lever has a mechanical advantage.

To calculate just how much mechanical advantage, we use the expression below.

Mechanical advantage = 3000/300

=> 10

Look at the lever system on the right. A load of 30N is supported by a 10N effort. What is its mechanical advantage?

Scan the image for the answer

Mechanical advantage is 3.

Stephen pushes down with a force of 60N to just lift the load off the ground. What is the mechanical advantage of the lever?

Scan the image for the answer

Mechanical advantage is 5.

Stephen pushes down with a force of 300N to just lift the load off the ground. What is the mechanical advantage of the lever?

Scan the image for the answer

Mechanical advantage is 10

Bolt cutters can deliver a staggering force of 20 kilonewtons, that is the equivalent of around 2,040 kilograms. 

It is even more impressive when you think that this is done by the person only applying a force on the handles equivalent to 25 kilograms or 250 kilonewtons.    

Look at the animation on the right. Suggest how this magnification of force is achieved.

Second order levers

A lever that has the load between the fulcrum and the effort is known as a second order lever.

Once again, the further away the effort is from the fulcrum and the load the greater the mechanical advantage of the lever.

Explain why a wheel barrow and a nutcracker are examples of second order levers.

Identify the fulcrum, load and effort.    

Identify the fulcrum, load and effort.

Third order levers

A third order lever is one which has the effort between the fulcrum and the load.

Such levers do not have good mechanical advantage. 

In fact they have mechanical disadvantage. The effort is closer to the fulcrum than the load. 

The effort is always greater than the load. 

However, one advantage of such levers is that the distance moved by the load is greater than the distance moved by the effort. 

Cranes such as the one on the left are examples of third order levers. 

As you can see the effort is between the load, at the top, and the fulcrum. 

The advantage of this lever system is that the load moves through a greater distance than the effort. 

This is desirable when the crane needs to lift loads high above the ground.

Tweezers are another example of a third order lever.

Look at the image on the left. Identify the fulcrum, load and effort.

Is the arm an example of a third order lever? Explain.

http://www.dynamicscience.com.au/tester/solutions1/hydraulicus/simplemachineslevers4.htm