5.7 Forces

Question 1

What is kinetics?

Answer 1

The study of forces that make the body move

Question 2

Why does motion occur?

Answer 2

Because a force (push or pull) is applied to the body

Question 3

What are the two important features of every force?

Answer 3

Magnitude (strength of force) and direction (line along which force is applied)

Question 4

According to Newton’s second law, what determines force?

Answer 4

Force = mass × acceleration

Question 5

What does Newton’s second law mean in practice?

Answer 5

Heavier objects or faster movements require more force

Question 6

What are the four main forces acting on the body?

Answer 6

Gravity, muscles, external resistance, friction

Question 7

What does gravity do in relation to the body?

Answer 7

It is the constant force that gives objects and body parts their weight

Question 8

What is an example of increasing gravitational pull on a limb?

Answer 8

Adding a dumbbell or cast

Question 9

How do muscles create force?

Answer 9

By actively contracting or passively stretching

Question 10

What are examples of external resistance?

Answer 10

Exercise bands, weights, manual resistance, everyday objects (like doors or windows)

Question 11

What is friction?

Answer 11

Resistance between two surfaces that can help provide stability or hinder movement

Question 12

What happens if friction is too little?

Answer 12

Movement becomes unstable (e.g., slipping on a tile floor)

Question 13

What is mass?

Answer 13

The amount of matter in something; it does not change based on location

Question 14

What is weight?

Answer 14

The force of gravity pulling on mass; it changes depending on gravity

Question 15

Does mass change if you go to the Moon or Mount Everest?

Answer 15

No, mass stays the same

Question 16

Does weight change if you go to the Moon or Mount Everest?

Answer 16

Yes, weight changes because gravity is different

Question 17

What is a moment in biomechanics?

Answer 17

The turning effect created when a force is applied at some distance from a joint or axis of rotation

Question 18

What is a moment arm?

Answer 18

The distance between where the force is applied and the axis of rotation

Question 19

How does a longer moment arm affect torque?

Answer 19

It produces more effort or torque

Question 20

How does a shorter moment arm affect torque?

Answer 20

It produces less torque

Question 21

Why does joint position matter in rehab and exercise?

Answer 21

Because changing the moment arm changes how hard the muscles must work

Question 22

Example: Why is lifting a weight with a straight leg harder than with a bent knee?

Answer 22

Because the moment arm is longer when the leg is straight, increasing torque demands