Levers - Third Class Levers

Question 1

What are the 3 types of levers?

Answer 1

1. First class levers
2. Second class levers
3. Third class levers

Question 2

What are the 3 components that each lever has

Answer 2

1. Force
2. Axis
3. Resistance

Question 3

Any projectile that utilises a lever is from what type of lever?

Answer 3

A third class lever

Not all third class levers create projectiles though

Question 4

Describe the orientation of third class levers

Answer 4

Axis - Force - Resistance

Force being in the middle is the key point

Question 5

What characteristic for third class levers posess?

Answer 5

They are speed multipliers

Question 6

What is the force arm?

Answer 6

The measure between point of force and axis point

Question 7

What is the resistance arm?

Answer 7

The measure between point of resistance and axis point

Question 8

Which is always bigger in third class levers; resistance arm or force arm?

Answer 8

Resistance arm

Question 9

What is Mechanical advantage?

Answer 9

Force arm divided by Resistance arm

Force arm/resistance arm

Question 10

State the mechanical advantage range for all third class levers

Answer 10

Always less than 1

As force arm is always smaller than resistance arm

Question 11

Describe the relationship between mechanical advantage and speed multiplier for third class levers

Answer 11

The smaller the mechanical advantage the greater the speed multiplier

Question 12

Describe amount of force in relation to resistance for third class levers

Answer 12

you need greater force to move a given resistance

Question 13

Describe the relationship between the resistance arm and the mechanical advantage and hence the benefits

Answer 13

• Longer resistance arm = lower mechanical advantage
• = Greater range of motion
• = Greater radius of rotation
• = Greater angular speed at end of lever

Question 14

How would you ideally set up a Third Lever based question focused on extending resistance arm

Answer 14

1. All third class levers are speed multipliers
2. They alll have a mechanical advantage of less than 1
3. A longer resistance arm would allow for lower mechanical advantage
4. Which means increased range of motion and increased speed at end of lever
5. Allowing [projectile] to be hit/propelled at maximal force and speed

Question 15

How would a person with longer legs have a greater advantage in kicking a ball further than person with shorter legs, referencing levers

Answer 15

• Kicking a ball would use a third class lever
• All third class levers are speeed multipliers
• A longer resistance arm of a longer limb/leg would lead to a lower mechanical advantage
• Hence, increased range of motion and increased speed at end of lever
• Thus, ball will be kicked at maximal speed and force.

Question 16

Give some examples of Third Class levers in human body working

Answer 16

• Bicep curl (concentric action)
• Kicking ball
• Throwing projectile

Question 17

In a bicep curl, if the force is produced by bicep, axis is elbow and resistance is weight, how is force in the middle of resistance and axis?

Answer 17

• All forces produced by muscles are considered at their attachment point
• Bicep crosses over join and attaches at radius
• Hence, attachment point is between axis and resistance