3. Calculations and External Forces Flashcards
What is a force?
A push or pull that alters or tends to alter the state of motion of a body.
What is velocity?
The rate of change in displacement.
What is momentum?
The quantity of motion possessed by a moving body.
What is acceleration?
The rate of change of velocity
Force equation
Force = mass x acceleration
Velocity equation
velocity = displacement//time taken
Momentum equation
momentum = mass x velocity
What is force measured in?
N
What is velocity measured in?
m/s
What is momentum measured in?
kgm/s
What is acceleration measured in?
m/s/s
What are the vertical forces?
Weight
Reaction force
What is weight?
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
What is weight represented by?
downward arrow
What is reaction force?
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
What is reaction force represented by?
upward arrow
What are the horizontal forces?
- friction
- air resistance
What is friction?
Opposes the motion when 2 surfaces are in contact and is measured in Newtons (N).
What is an example of friction in play?
a cyclist’s tyres would tend to slip backwards as they rotate, friction opposes this and acts forward
What are the factors that affect friction?
- roughness of the ground
- roughness of the contact surface
- temperature
- size of normal reaction
How does roughness of the ground affect friction?
By increasing roughness of the ground, surface friction is increased.
Example of roughness of ground affecting friction
athletes run on a rubberised track
How does roughness of the contact surface affect friction?
By increasing roughness of contact surface, friction is increased.
Example of roughness of contact surface affecting friction
sprinters, jumpers, throwers wear spikes
How does temperature affect friction?
By increasing the temp, of the ground and contact surface, friction is increased
Example of temperature affecting friction
F1 drivers have a warm up lap on the track
How does the size of normal reaction affect friction?
By increasing the normal reaction, friction is increased.
Example of size of normal reaction affecting friction
Shot putters have a high mass
What is air resistance?
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
What are the factors affecting air resistance?
- velocity
- shape
- frontal cross-sectional area
- smoothness of the surface
How does velocity affect air resistance?
By increasing velocity, air resistance increases
Example of how velocity affects air resistance
The greater the velocity of a sprint cyclist around the velodrome track, the greater the force of air resistance opposing their motion.
How does shape affect air resistance?
The more aerodynamic the shape, the lower the air resistance.
Many sports use a tear drop or aerofoil shape to minimise air resistance.
Example of how shape affects air resistance
shape of a sprint cyclist’s helmet - streamlined
What does streamlined mean?
The creation of smooth air flow around an aerodynamic shape to minimise air resistance
How does frontal cross sectional area affect air resistance?
By decreasing the frontal cross sectional area, air resistance decreases
Example of how frontal cross sectional area affects air resistance
The low, crouched position of giant slalem skiers in the straights
How does smoothness of surface affect air resistance?
By increasing smoothness of the surface, air resistance decreases
Example of smoothness of surface affects air resistance
Smooth lycra suits of sprinters, cyclists, skiers
