Physics Kinetics and Motion

Questions and Answers

Which position of the weight cuff would require more effort at the shoulder joint to move it through its range of motion, at the wrist or at the elbow? Explain your reasoning.

The cuff positioned at the wrist requires more effort because it increases the distance from the shoulder joint, creating a greater torque.

If two people with the same weight and Base of Support (BOS) are compared, one on stilts and the other not, who is more stable and why?

The person not on stilts is more stable because their BOS is lower to the ground, providing better equilibrium.

What type of force would be exerted by two people pulling on a draw sheet to move a patient toward them?

The force would be classified as a force couple, as they are exerting forces in opposite directions.

Before moving a patient, what can the two people do to increase their own stability?

They can widen their Base of Support and lower their center of gravity to enhance stability. Signup and view all the answers

How do the two heads of the gastrocnemius contribute to resultant force?

The two heads of the gastrocnemius generate a combined force that acts to plantarflex the ankle joint. Signup and view all the answers

Why is it more difficult for a person in a wheelchair to balance on only the back wheels?

It is more difficult due to a reduced Base of Support and a higher center of gravity, which makes balance precarious. Signup and view all the answers

What biomechanical factor is affected when a cuff is moved from the elbow to the wrist?

The torque generated by the shoulder joint changes due to the difference in moment arm length. Signup and view all the answers

In which scenario would a person have a higher risk of losing balance, standing on stilts or on flat ground?

Standing on stilts presents a higher risk of losing balance due to elevated center of gravity and narrower BOS. Signup and view all the answers

What role do the sternal and clavicular portions of the pectoralis major play when lifting an object?

They assist in shoulder flexion, adduction, and internal rotation during the lifting motion. Signup and view all the answers

What happens to the forces acting on a patient when two caregivers pull a draw sheet?

The forces act in parallel but result in a linear movement of the patient towards them. Signup and view all the answers

Study Notes

Motion and Forces

Acceleration signifies any change in velocity, impacting an object's speed or direction.
Mass quantifies inertia, determining an object's resistance to motion changes.
Kicking a soccer ball harder increases its travel distance according to Newton’s second law of motion (law of acceleration).

Kinetics and Torque

Kinetics explains motion relative to its causes, with torque referring to the force's capability to induce rotation around an axis.
Muscle contractions create motion around joint axes, evidencing torque in action.
Friction between surfaces influences motion, as demonstrated when sliding on different flooring types.

Force and Direction Changes

Changing an object's direction necessitates force; the degree of change correlates with the force's magnitude.
Torque is the product of force and the distance from the axis of rotation, represented by the moment arm.

Force Couples

A force couple exists when multiple forces act in different directions, inducing a rotational effect.
Example: Upper and lower trapezius muscles, along with serratus anterior, work together to rotate the scapula.

Understanding Torque

Torque functionality is influenced by force magnitude and the moment arm's length.
A wrench exemplifies torque, where twist force increases via greater handle force or an extended handle length.

Lever Systems in the Body

There are fewer second-class levers in the body, exemplified by ankle plantar flexor function during tiptoe standing.
This lever system prioritizes power; a small muscle force can counteract larger resistance despite limited distance of motion.

Basic Rules of Simple Machines

The principle of simple machines states any gain in power corresponds with a loss in motion distance; raising weight efficiently limits vertical travel.

Review Questions Highlights

Positioning a weight cuff affects effort at the shoulder joint based on resistance leverage.
Stability comparison between individuals on stilts and those without considers center of gravity and base of support.
Understanding resultant forces is pivotal in collaborative movement applications, like assisting a patient transfer.

Description

This quiz covers the principles of kinetics, mass, and acceleration in physics. It explores how motion and resistance to change affect the travel distance of objects, such as a soccer ball. Test your understanding of these fundamental concepts of motion.