grade 8 unit 4 mechanical systems topic 1: levers and inclined planes

Grade 8 Unit 4 Mechanical Systems

Topic 1: Levers and Inclined Planes

Lever

Lever

Fulcrum

A lever is a simple machine that changes the amount of force you must exert in order to move an object. A lever consists of a bar that is free to rotate around a fixed point known as the fulcrum.

Lever

The fulcrum is the point of the lever that does not move; the lever’s point of rotation.

The fulcrum supports the lever.

Lever

The effort force is the force applied on a lever to make it move.

The term “effort force” is also used to describe the force supplied to any machine in order to produce an action.

Lever

The load is the mass of an object that is moved or lifted by a machine. The load is also the resistance to movement that a machine must overcome.

Lever

The effort arm is the distance between the fulcrum and the effort force.

In a similar fashion, the load arm is the distance between the fulcrum and the load.

Levers

Levers are sorted into three classes. The class a lever belongs to depends on the position of the effort force (E), fulcrum (F) or load (L).

Levers are classified by whichever of theses three factors is in the middle.

Effort EffortEffort

In a Class 1 lever, the fulcrum (F) is in the middle.

Its advantage is that it can be used for power or precision (it also changes direction of the force). An example is a pair of scissors.

Class 1 Lever

Class 2 Lever

In a Class 2 lever, the load (L) is in the middle.

Its advantage is that it increases the effort force on the load. An example is a wheelbarrow.

Class 3 Lever

In a Class 3 lever, the effort (E) is in the middle.

Its advantage is that the load can be moved very quickly. An example is a hockey stick.

Lever ID

F

L

E

Class 1 lever

Lever ID

F

L

E

Class 3 lever

Lever ID

F L

E

Class 2 lever

Lever ID

F

L

E

Class 3 lever

Lever ID

F

L

E

Class 1 lever

Lever ID

F

LE

Class 2 lever

Lever ID

E

L

F

Class 1 lever

Lever ID

EL

F

Class 3 lever

Lever ID

EL

FClass 3 lever

Lever ID

For most people the class that is the hardest to classify is Class 3, because it is difficult to determine where the effort force (E) is.

Bones and Muscles: Built-in Levers

In the human body, the bones act as levers and your joints acts as a fulcrum. Your tendons and muscles exert the effort force on the bone. The load might be something you are lifting or pulling or your own body.

Bones and Muscles: Built-in Levers

Most of the levers in your body are class 3, but the other types of levers are observable as well.

The head and neck form a class 1 lever.

Bones and Muscles: Built-in Levers

The flexing of the foot illustrates a class 2 lever.

F

L

E

Bones and Muscles: Built-in Levers

The arm illustrates a class 3 lever.

F

L

E

Bones and Muscles: Built-in Levers

The tip-toe maneuver illustrates a class 2 lever.

F

L

E

Bones and Muscles: Built-in Levers

The arm-lifting maneuver illustrates a class 2 lever.

F

L

E

Bones and Muscles: Built-in Levers

The arm-pulling maneuver illustrates a class 1 lever.

E

LF

Bones and Muscles: Built-in Levers

Bones and Muscles: Built-in Levers

An Arm in Space

Levers were used in the Space Shuttle Program and on the International Space Station in the form of the Remote Manipulator System. It is better known as the Canadarm. It received that name because it was made in Canada and it works like an arm.

An Arm in Space

It is 15 m long and 38 cm in diameter. While its own mass is 450 kg, it can deploy payloads up to 266 tonnes in space. On the Earth, it cannot lift its own weight. It has joints that resemble the shoulder, elbow and wrist of a person.

An Arm in Space

The Canadarm was a valuable addition to the space shuttle program because it helped to launch and recover satellites and to help with repairs of objects in space.

Although the Space Shuttle program is now finished, the Candarm is still in use in space.

An Arm in Space

Sixteen countries, including Canada, are co-operating in the planning and assembling of the International Space Station (ISS). The Canadarm 2 is helping construct and maintain the ISS.

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