Force

Force definition

push or pull which causes object to change its state of motion

Internal force

contraction of skeletal muscle

External force

comes from outside the body
eg. friction

5 effects force has on the body

-creates motion
-accelerate a body
-decelerate a body
-change direction
-change shape of a body

What is net force?

overall force that will act on a body when all individual forces have been considered

What factors does net force consider?

-air resistance
-friction
-weight
-reaction

Vertical forces

-weight
-reaction

What is weight?

gravitational pull
downward from centre of mass

What is the equation for weight?

Mass(kg) X acceleration due to gravity (m/s/s)

What is reaction?

equal and opposite force
in response to action force placed on it
extends upwards from point of contact

What is friction?

opposes motion of 2 surfaces sliding over one another, acts parallel to 2 surfaces in contact

Factors that affect frcition

-roughness of ground surface
-roughness of contact surface
-temperature
-size of normal reaction

What is air resistance?

Is a force that opposes motion of body
against direction of motion from centre of mass

Factors that affect air resistance

-velocity
-shape
-front cross-sectional area
-smoothness of surface

Balanced forces - what is it?

Net force is 0
no change in motion

Unbalanced forces - what is it?

there is a net force, results in change of motion
forces are unequal
If net force positive it will accelerate