Lesson 3 - Levers

Question 1

What 2 functions do levers have?

Answer 1

1 - To apply force (strength) to an object.
The longer the effort arm, the greater the force generated.

2 - To move the load a greater distance or through a greater range of movement.
The shorter the effort arm, the greeater the distance moved

Question 2

1 2 3

Answer 2

F R E

Question 3

First Class Levers:

Answer 3

• Fulcrum is located in the middle between the load and the effort.
• Only occurs at elbow extension
• E.g., tricep dips

Question 4

Second Class Levers:

Answer 4

• Laod is located in the middle betweem the fulcrum and the effort.
• Only occurs during plantarflexion
• E.g., baksketball shot

Question 5

Third Class Levers:

Answer 5

• Effort is in the middle between the fulcrum and the load.
• This is the most common form of lever in the human body.
• E.g., kicking a football.

Question 6

What are the 2 benefits of levers?

Answer 6

• Large loads can be moved with a relatively small amount of effort.
• The distance a load can be moved, or the speed with which it can be moved, can be increased without an increase in effort.

Question 7

What is the load arm?

Answer 7

The distance from the load to the fulcrum

Question 8

What is the effort arm?

Answer 8

The distance from the effort to the fulcrum

Question 9

What is mechanical advantage?

Answer 9

• When a lever’s effort arm is longer than its load arm it is said to have a mechanical advantage.
• Levers with a mechanical advantage can move large loads with less effort.
• 2nd class levers always have a mechanical advantage.

Question 10

Use the sporting example of a long jump to suggest that 2nd class levers have a mechanical advantage.

Answer 10

• This example of a 2nd class lever has a mechanical advantage because the effort arm is longer than the laod arm.
• The effort produced by the muscles, which is relatively small, is able to drive the fill weight of the athlete off the ground.

Question 11

What is mechanical disadvantage?

Answer 11

• When a lever’s load arm is longer than its effort arm it is a mechanical disadvantage.
• Whilst they are said to be a ‘disadvantage’, third class levers are able to increase the speed at the end of the lever arm.
• 3rd class levers always have a mechanical disadvantage.

Question 12

Use the hip joint to suggest that the 3rd class levers have a mechanical disadvanatge.

Answer 12

• The hip joint is at the ‘disadvantage’ as it has to apply a greater force to lift the load.
• 3rd class levers can take a small movement near the fulcrum and make a large movement where the load is. This provides a large range of movement and a high speed being produced.

Question 13

How is the mechanical adv/disadvantage determined in a 1st class lever?

Answer 13

• With the first class lever, the position of the fulcrum is key.
• If the fulcrum is closer to the load, then a small amount of effort will result in more powerful movements of load.
• If the fulcrum is closer to the effort, more effort is needed to move the load, but it can be moved at a higher speed.

Question 14

Summary of the efects/benefits of levers…

Answer 14

• 1st class - can increase both effort and speed of a body.
• 2nd class - tend to only increase the effect of the effort force.
• 3rd class - can be used to increase the speed of a body.