Physics - week 2

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Questions and Answers

What happens to the translatory component of muscle force at 90 degrees of elbow flexion?

It is directed towards the joint.

It is directed away from the joint.

It is larger than the rotatory component.

It is equal to the rotatory component. (correct)

Which component of muscle force contributes to joint stability?

Compression component (correct)

Rotatory component

Translatory component

Distraction component

What is the effect of angle on the magnitude of force applied to a lever?

Less torque is produced at angles other than 90 degrees. (correct)

It increases torque at all angles.

Torque is maximized at 180 degrees.

Torque remains constant regardless of the angle.

What characteristic distinguishes a rotatory component from a translatory component of muscle force?

It tries to turn a body segment around the joint. Signup and view all the answers

At what angle does the translatory component become equal to zero?

90 degrees of elbow flexion Signup and view all the answers

Which term describes a force that separates the joint surfaces?

Distraction component Signup and view all the answers

What is the most effective angle for a force to be applied to generate torque?

90° Signup and view all the answers

What occurs when muscle force is applied at an angle less than 90 degrees?

Less torque is produced than at 90 degrees. Signup and view all the answers

What effect does elbow flexion have on the directional nature of the translatory component?

It changes direction during the course of flexion. Signup and view all the answers

What happens to torque efficiency when the angle of pull deviates from 90°?

It decreases. Signup and view all the answers

In the context of human biomechanics, what does 'torque' refer to?

A force that tends to produce rotation. Signup and view all the answers

What defines the mechanical axis of a bone?

A straight line connecting the midpoints of the joints at both ends of the bone. Signup and view all the answers

Why does a translatory force at elbow flexion angles of 35° and 145° affect the joint differently?

At 35°, it compresses, while at 145°, it creates distraction. Signup and view all the answers

How do anatomic pulleys affect muscle force?

They change the direction of the force without altering its magnitude. Signup and view all the answers

Which statement is true regarding the angle of pull of a muscle?

It is the angle between the vector of muscle force and the straight line from the joint's center of rotation to the muscle insertion. Signup and view all the answers

What is the consequence of a muscle's angle of pull being less than 90°?

Some force is used to pull the insertion towards the joint. Signup and view all the answers

How does an anatomic pulley assist in generating torque?

It changes the angle of pull while maintaining force magnitude. Signup and view all the answers

At what angle does a muscle's insertion produce maximum torque?

90° Signup and view all the answers

What does the angle of pull need to be for maximum torque generation in a lever?

Right angle of 90° Signup and view all the answers

What aspect of muscle mechanics do anatomic pulleys optimize?

Direction of muscle force Signup and view all the answers

Study Notes

Muscle Force & Components

Muscle force (Fms) is the force that a muscle exerts on a bone.
Muscle force can be broken down into two components: rotatory component (fr) and translatory component (ft).
Rotatory Component (fr) is the force perpendicular to the bone, which causes rotation around the joint. It creates torque.
Translatory Component (ft) is the force parallel to the bone, which affects the stability of the joint. It can either compress (push together) or distract (pull apart) the joint surfaces.
The angle of pull affects the magnitude of fr and ft.
At 90 degrees, fr is maximized, and ft is zero.
As the angle of pull deviates from 90 degrees, fr decreases, and ft increases.

Importance of Rotatory Component

When a force is applied at 90 degrees, the rotational component is maximized because it equals the total force.
At angles other than 90 degrees, the rotational component (torque) is less, as part of the force contributes to translation.

Angle of Pull of a Muscle

The angle of pull is the angle between the line of pull of the muscle and the mechanical axis of the bone.
The mechanical axis is a straight line connecting the midpoints of the joints at both ends of the bone.
Maximum torque is produced when the muscle pulls at a 90-degree angle to the bone.
Efficiency decreases as the angle of pull deviates from 90 degrees.

Anatomic Pulleys

A bony prominence or structure can change the direction of muscle pull.
This is called an anatomic pulley.
Pulleys do not change the magnitude of force but improve the ability to generate torque by altering the line of action.

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Description

Explore the dynamics of muscle force and its two primary components: the rotatory and translatory components. Understand how the angle of pull influences these forces and their effect on joint stability. This quiz will help reinforce your knowledge of how muscles interact with bones during movement.