3. Calculations and External Forces

Question 1

What is a force?

Answer 1

A push or pull that alters or tends to alter the state of motion of a body.

Question 2

What is velocity?

Answer 2

The rate of change in displacement.

Question 3

What is momentum?

Answer 3

The quantity of motion possessed by a moving body.

Question 4

What is acceleration?

Answer 4

The rate of change of velocity

Question 5

Force equation

Answer 5

Force = mass x acceleration

Question 6

Velocity equation

Answer 6

velocity = displacement//time taken

Question 7

Momentum equation

Answer 7

momentum = mass x velocity

Question 8

What is force measured in?

Answer 8

N

Question 9

What is velocity measured in?

Answer 9

m/s

Question 10

What is momentum measured in?

Answer 10

kgm/s

Question 11

What is acceleration measured in?

Answer 11

m/s/s

Question 12

What are the vertical forces?

Answer 12

Weight
Reaction force

Question 13

What is weight?

Answer 13

The gravitational pull that the earth exerts on a body and is measured in Newtons.
Weight force is always present and acts downwards from the body’s centre of mass

Question 14

What is weight represented by?

Answer 14

downward arrow

Question 15

What is reaction force?

Answer 15

The equal and opposite force exerted by a body in response to the action force placed upon it and measured in Newtons.
Newtons 3rd law of motion and is always present when two bodies are in contact

Question 16

What is reaction force represented by?

Answer 16

upward arrow

Question 17

What are the horizontal forces?

Answer 17

• friction
• air resistance

Question 18

What is friction?

Answer 18

Opposes the motion when 2 surfaces are in contact and is measured in Newtons (N).

Question 19

What is an example of friction in play?

Answer 19

a cyclist’s tyres would tend to slip backwards as they rotate, friction opposes this and acts forward

Question 20

What are the factors that affect friction?

Answer 20

• roughness of the ground
• roughness of the contact surface
• temperature
• size of normal reaction

Question 21

How does roughness of the ground affect friction?

Answer 21

By increasing roughness of the ground, surface friction is increased.

Question 22

Example of roughness of ground affecting friction

Answer 22

athletes run on a rubberised track

Question 23

How does roughness of the contact surface affect friction?

Answer 23

By increasing roughness of contact surface, friction is increased.

Question 24

Example of roughness of contact surface affecting friction

Answer 24

sprinters, jumpers, throwers wear spikes

Question 25

How does temperature affect friction?

Answer 25

By increasing the temp, of the ground and contact surface, friction is increased

Question 26

Example of temperature affecting friction

Answer 26

F1 drivers have a warm up lap on the track

Question 27

How does the size of normal reaction affect friction?

Answer 27

By increasing the normal reaction, friction is increased.

Question 28

Example of size of normal reaction affecting friction

Answer 28

Shot putters have a high mass

Question 29

What is air resistance?

Answer 29

A force that opposes the motion of a body travelling through the air and is a form of fluid friction measured in Newtons. It can play a huge role in sport, especially for bodies that travel at high velocities such as a badminton shuttle

Question 30

What are the factors affecting air resistance?

Answer 30

- velocity - shape - frontal cross-sectional area - smoothness of the surface

Question 31

How does velocity affect air resistance?

Answer 31

By increasing velocity, air resistance increases

Question 32

Example of how velocity affects air resistance

Answer 32

The greater the velocity of a sprint cyclist around the velodrome track, the greater the force of air resistance opposing their motion.

Question 33

How does shape affect air resistance?

Answer 33

The more aerodynamic the shape, the lower the air resistance. Many sports use a tear drop or aerofoil shape to minimise air resistance.

Question 34

Example of how shape affects air resistance

Answer 34

shape of a sprint cyclist's helmet - streamlined

Question 35

What does streamlined mean?

Answer 35

The creation of smooth air flow around an aerodynamic shape to minimise air resistance

Question 36

How does frontal cross sectional area affect air resistance?

Answer 36

By decreasing the frontal cross sectional area, air resistance decreases

Question 37

Example of how frontal cross sectional area affects air resistance

Answer 37

The low, crouched position of giant slalem skiers in the straights

Question 38

How does smoothness of surface affect air resistance?

Answer 38

By increasing smoothness of the surface, air resistance decreases

Question 39

Example of smoothness of surface affects air resistance

Answer 39

Smooth lycra suits of sprinters, cyclists, skiers