Biomechanical Principles, external factors and free body diagrams

Question 1

What are Newton’s three laws

Answer 1

1st law - law of inertia
2nd law - law of acceleration
3rd law - law of reaction

Question 2

Define Newton’s first law of inertia

Answer 2

A body will remain in a state of rest or uniform velocity unless acted on by an external or unbalanced force

Question 3

Define Newton’s second law of acceleration

Answer 3

The acceleration of a body is proportional to the size of the force applied and takes place in the direction at which the force acts

Question 4

Define Newton’s third law of reaction

Answer 4

For every action there is an equal and opposite reaction. The reaction force is equal in size and opposite in direction to the action force

Question 5

Give a sporting example of Newton’s first law of inertia

Answer 5

A football will remain at rest on the penalty spot until a force is applied to the ball by the players foot

Question 6

Give a sporting example of Newton’s second law of acceleration

Answer 6

The acceleration of a netball during a pass is proportional to the force from the muscle and is in the same direction of the force

Question 7

Name a sporting example of Newton’s third law of reaction

Answer 7

When serving, a tennis player pushes downwards on the ground (action force) and the ground pushes upward on the player (reaction force)

Question 8

Define force

Answer 8

Force is a push or pull that tends to alter the state of motion of the body

Question 9

Define balanced forces

Answer 9

When two or more forces acting on the body are equal in size and in opposite directions they cancel out

Question 10

Define unbalanced force

Answer 10

When two or more forces acting on the body do not cancel out so a net force acts upon the body

Question 11

Define net force

Answer 11

Also known as the resultant force, this is the overall force acting on a body when all forces are considered

Question 12

Where do external forces originate from

Answer 12

Outside the body

Question 13

What are the 4 external forces

Answer 13

Weight, reaction, friction and air resistance

Question 14

Define weight

Answer 14

The force that acts directly downwards from the centre of mass

Question 15

Define reaction

Answer 15

Reaction force acts upwards from the point(s) of contact with the ground in reaction to all forces

Question 16

Define friction

Answer 16

Friction opposes the sliding motion of one surface across another

Question 17

Define air resistance

Answer 17

Air resistance acts against the direction of motion opposing the movement of the body through the air

Question 18

What are the 4 factors effecting friction

Answer 18

1. Characteristics/roughness of surface 1 (sole of footwear)
2. Characteristics/roughness of surface 2 (playing surface)
3. Force/normal ground reaction force (the force pushing the two surfaces together)
4. Temperature (heated tyres increase friction)

Question 19

State 3 ways in which friction can be maximised

Answer 19

1. Increase the roughness of surfaces
2. Increase the mass/downforce (heavy props)
3. Increase the temperature of materials

Question 20

State one way in which you can minimise friction

Answer 20

Increase the smoothness of surfaces

Question 21

State the 4 factors that effect air resistance

Answer 21

1. Velocity of person/object
2. Frontal cross section of object
3. Streamline/shape of object
4. Surface characteristics

Question 22

State three ways in which air resistance can be minimised

Answer 22

1. Reduce the frontal cross sectional area
2. Using a streamline shape
3. Making surfaces smoother

Question 23

Where does weight originate from

Answer 23

Centre of mass

Question 24

Which direction does weight act upon

Answer 24

Vertically downwards

Question 25

How long is the arrow for weight

Answer 25

Proportional to the objects mass

Question 26

Where does reaction originate from

Answer 26

All points of contact with the ground

Question 27

Which direction do reaction forces act

Answer 27

Upwards perpendicular to the ground

Question 28

How long are the arrows representing reaction

Answer 28

Equal but opposite to all downwards acting forces

Question 29

Where does air resistance originate from

Answer 29

Centre of mass

Question 30

Which direction does air resistance act

Answer 30

Opposite to the direction of motion

Question 31

How long is the arrow representing air resistance

Answer 31

Proportional to velocity and other factors effecting air resistance

Question 32

Where does friction originate from

Answer 32

All points of contact with the ground

Question 33

Which direction does friction act

Answer 33

In the direction of motion

Question 34

How long are the arrow representing friction

Answer 34

Proportional to the factors effecting friction