IB Sports, exercise and health science Topic B.1.4.1 Classes of Levers and Their Applications in Human Movement and Sport Revision Notes (SL/HL)

IB Sports, exercise and health science Topic B.1.4.1 Classes of Levers and Their Applications in Human Movement and Sport Revision Notes (SL/HL) | RevisionDojo

Written by official IB examiners

Levers explain how force moves loads in sport

Definition

Lever

A lever is a rigid structure that rotates around a fixed point called the fulcrum. Levers are used to move a load (resistance) by applying an effort (force). The relative positions of the fulcrum, load, and effort determine the type of lever and its mechanical advantage or disadvantage.

Levers are rigid rods that rotate around a fulcrum (pivot point) when a force is applied.
The purpose of a lever is to move a load or resistance, such as a weight or another object.

Note

In the human body, bones act as levers, joints as fulcrums, and muscles provide the effort.

Every lever has a fulcrum, effort, and load

A lever consists of three main components.

1. Fulcrum

The fulcrum is the fixed point around which the lever rotates or pivots.
It is the axis of movement and does not move itself.
In human anatomy, joints typically serve as the fulcrum in lever systems.

Example

In a seesaw, the fulcrum is the pivot point in the middle.
In the human body, the elbow joint acts as the fulcrum in many upper limb movements.

2. Effort

The effort is the force applied to the lever to move the load.
In the body, this force comes from muscle contraction.
The effort is applied at a point on the lever and generates the force needed for movement.

Example

In a bicep curl, the bicep muscle contracts to apply effort in lifting the weight.
The effort is applied at the forearm, which then moves the load (the weight).

3. Load

The load is the resistance or the weight being moved by the lever.
In the body, the load could be an external object, like a dumbbell, or a body part, such as the forearm when lifting an object.

Example

During a calf raise, the **weight of the body** (as the load) is lifted by the action of the calf muscle (the effort), with the **ball of the foot** acting as the fulcrum.

Example

Door operation demonstrates a lever system with identifiable fulcrum, effort, load, and moment arms.

Fulcrum: Hinges
Effort: Push/pull on handle
Load: Door weight
Moment arms: Door width and handle position

Mechanical advantage depends on effort arm and load arm

Definition

Mechanical Advantage

The ratio between effort and load that determines a lever's efficiency

The mechanical advantage of a lever refers to its ability to amplify the force applied to it.
This is determined by the ratio of the lengths of the effort arm to the load arm.
The longer the effort arm, the greater the mechanical advantage, making it easier to move a heavy load with less force.

Mechanical advantage is calculated from effort arm and load arm

The mechanical advantage of a lever is given by the formula:

Mechanical Advantage (MA) = Length of Effort Arm / Length of Load Arm

Effort arm: Distance from the fulcrum to the point where the effort is applied.
Load arm: Distance from the fulcrum to the point where the load is applied.

Example

In a second-class lever, the effort arm is longer than the load arm, giving the lever a mechanical advantage that makes lifting easier, despite using less force.

Note

Higher MA: The effort required to move a load is reduced, but the range of motion and speed of movement are also reduced.
Lower MA: The effort increases, but the range of motion and speed increase, making the movement faster.

Lever class depends on the position of fulcrum, effort, and load

Levers are classified into three types based on the relative positions of the effort, fulcrum, and load:

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Lorem ipsum dolor sit amet, consectetur adipiscing elit.
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Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris.
Duis aute irure dolor in reprehenderit in voluptate velit esse cillum.

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Levers explain how force moves loads in sport

Definition

Lever

Levers are rigid rods that rotate around a fulcrum (pivot point) when a force is applied.
The purpose of a lever is to move a load or resistance, such as a weight or another object.

Note

In the human body, bones act as levers, joints as fulcrums, and muscles provide the effort.

Every lever has a fulcrum, effort, and load

A lever consists of three main components.

1. Fulcrum

The fulcrum is the fixed point around which the lever rotates or pivots.
It is the axis of movement and does not move itself.
In human anatomy, joints typically serve as the fulcrum in lever systems.

Example

In a seesaw, the fulcrum is the pivot point in the middle.
In the human body, the elbow joint acts as the fulcrum in many upper limb movements.

2. Effort

The effort is the force applied to the lever to move the load.
In the body, this force comes from muscle contraction.
The effort is applied at a point on the lever and generates the force needed for movement.

Example

In a bicep curl, the bicep muscle contracts to apply effort in lifting the weight.
The effort is applied at the forearm, which then moves the load (the weight).

3. Load

The load is the resistance or the weight being moved by the lever.
In the body, the load could be an external object, like a dumbbell, or a body part, such as the forearm when lifting an object.

Example

During a calf raise, the **weight of the body** (as the load) is lifted by the action of the calf muscle (the effort), with the **ball of the foot** acting as the fulcrum.

Example

Door operation demonstrates a lever system with identifiable fulcrum, effort, load, and moment arms.

Fulcrum: Hinges
Effort: Push/pull on handle
Load: Door weight
Moment arms: Door width and handle position

Mechanical advantage depends on effort arm and load arm

Definition

Mechanical Advantage

The ratio between effort and load that determines a lever's efficiency

The mechanical advantage of a lever refers to its ability to amplify the force applied to it.
This is determined by the ratio of the lengths of the effort arm to the load arm.
The longer the effort arm, the greater the mechanical advantage, making it easier to move a heavy load with less force.

Mechanical advantage is calculated from effort arm and load arm

The mechanical advantage of a lever is given by the formula:

Mechanical Advantage (MA) = Length of Effort Arm / Length of Load Arm

Effort arm: Distance from the fulcrum to the point where the effort is applied.
Load arm: Distance from the fulcrum to the point where the load is applied.

Example

In a second-class lever, the effort arm is longer than the load arm, giving the lever a mechanical advantage that makes lifting easier, despite using less force.

Note

Higher MA: The effort required to move a load is reduced, but the range of motion and speed of movement are also reduced.
Lower MA: The effort increases, but the range of motion and speed increase, making the movement faster.

Lever class depends on the position of fulcrum, effort, and load

Levers are classified into three types based on the relative positions of the effort, fulcrum, and load:

Definition

Paywall

(on a website) an arrangement whereby access is restricted to users who have paid to subscribe to the site.

anim nostrud sit dolore minim proident quis fugiat velit et eiusmod nulla quis nulla mollit dolor sunt culpa aliqua

Duis aute irure dolor in reprehenderit

Note

Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam quis nostrud exercitation.

Excepteur sint occaecat cupidatat non proident

Tip

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Sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.
Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris.
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A.1 Communication3 subtopics

A.2 Hydration and nutrition3 subtopics

A.3 Response3 subtopics

B.1 Generating movement in the body4 subtopics

B.2 Forces, motion and movement3 subtopics

B.3 Injury2 subtopics

C.1 Individual differences2 subtopics

C.2 Motor learning2 subtopics

C.3 Motivation3 subtopics

C.4 Stress and coping2 subtopics

C.5 Psychological skills2 subtopics

IB Sports, exercise and health science B.1.4.1 Classes of Levers and Their Applications in Human Movement and Sport Notes

A.1 Communication3 subtopics

A.2 Hydration and nutrition3 subtopics

A.3 Response3 subtopics

B.1 Generating movement in the body4 subtopics

B.2 Forces, motion and movement3 subtopics

B.3 Injury2 subtopics

C.1 Individual differences2 subtopics

C.2 Motor learning2 subtopics

C.3 Motivation3 subtopics

C.4 Stress and coping2 subtopics

C.5 Psychological skills2 subtopics

Levers explain how force moves loads in sport

Every lever has a fulcrum, effort, and load

1. Fulcrum

2. Effort

3. Load

Mechanical advantage depends on effort arm and load arm

Mechanical advantage is calculated from effort arm and load arm

Lever class depends on the position of fulcrum, effort, and load

anim nostrud sit dolore minim proident quis fugiat velit et eiusmod nulla quis nulla mollit dolor sunt culpa aliqua

Duis aute irure dolor in reprehenderit

Excepteur sint occaecat cupidatat non proident

Unlock the rest of this chapter with a free account

Levers explain how force moves loads in sport

Every lever has a fulcrum, effort, and load

1. Fulcrum

2. Effort

3. Load

Mechanical advantage depends on effort arm and load arm

Mechanical advantage is calculated from effort arm and load arm

Lever class depends on the position of fulcrum, effort, and load

anim nostrud sit dolore minim proident quis fugiat velit et eiusmod nulla quis nulla mollit dolor sunt culpa aliqua

Duis aute irure dolor in reprehenderit

Excepteur sint occaecat cupidatat non proident

Unlock the rest of this chapter with a free account