Biomechanics Principles

Question 1

Newton 1/ Law of Inertia

Answer 1

A body will remain in a state of rest or uniform motion unless an external force acts upon it

Question 2

Newton 2 /Law of Acceleration

Answer 2

The acceleration or rate of change of momentum or velocity of a body is proportional to the size of the force and takes place in the direction in which the force acts

Question 3

Newton 3 /Law of Reaction

Answer 3

For every action or force there is an equal and opposite reaction

Question 4

What is meant by ‘balanced forces’?

Answer 4

2 (or more)(opposing) forces are equal (in size)
No change in motion
Constant velocity/rest occurs

Question 5

What is meant by ‘unbalanced forces’?

Answer 5

Two (or more)(opposing) forces are not equal (in size)
Change in motion
Acceleration/deceleration occurs

Question 6

Explain what is meant by the term ‘net force’

Answer 6

The sum of all forces acting on a body
Net force is zero if forces are balanced
Net force positive/negative if forces are unbalanced

Question 7

Describe how the force of weight acts on a sporting body

Answer 7

Downward force
Acts from centre of mass
Due to gravity

Question 8

Factors affecting air resistance

Answer 8

Velocity
Shape
Frontal cross sectional area
Surface characteristics
Air density

Question 9

Using examples from sport explainthreefactors affecting air resistance

Answer 9

Decreased frontal cross-sectional area = decrease in air resistancee.g.sprint cyclist tuck head and hands in and lift knees high
Shape – Aerofoil, an aerodynamic shape = decrease air resistancee.g.shape of a discus in flight
Surface characteristics - Smooth surface = decrease air resistancee.g.lycra suits of a speed skater / shaved down in cycling
Increased velocity = increased air resistancee.g.high speed of sprinter
Air density decrease = decrease ARe.g.drafting in cycling / javelin travels further at altitude

Question 10

Define the term ‘friction’ and describe, using sporting examples, how performers increase or decrease friction in order to optimise performance. (3)

Answer 10

The resistance to motion of two moving objects or surfaces that touch
Increased roughness of contact surface = increased friction e.g. sprinter wears spikes to increase friction which helps them run faster
Increased roughness of ground surface = increased friction e.g. tarmacadam track in athletics increases friction
Create down force - Spoiler on F1 car applies down force, increasing friction to increase speed
Increased temperature = increased friction e.g. F1 racing warm-up lap.

Question 11

Explain, using practical examples, why some performers would want to maximise friction. (2)

Answer 11

Maximise friction force to accelerate, e.g. sprinter wears spikes to aid grip when accelerating
Maximise friction to slow down/stop, e.g. a skier turns the skis sideways to slow down or stop
Increase friction to change direction, e.g. footballer wears studs to enable them to turn quickly
A performer increases friction to impart spin on an object, e.g. a slice shot in table tennis

Question 12

Define ‘acceleration’ and describethreeways in which a performer can increase their acceleration during sport or physical activity. (3)

Answer 12

Acceleration = rate of change of velocity
(Final velocity – initial velocity) ÷ time taken
Increase force - e.g. a sprinter can apply a greater force to the blocks/track
Increase friction - e.g. a long jumper can wear spikes to increase friction with the ground
Reduce mass - e.g. a high jumper loses weight prior to competition
Improve technique - e.g. a runner adjusts technique
Reduce air resistance e.g. a sprint cyclist adopts a streamlined shape to minimise air resistance