New tennis / table tennis balls in matches; table tennis balls / basketball checked and must bounce to a certain height; golf club / baseball bats limit CoR

Law of reaction - for every action there is an equal and opposite reaction

Freezing of baseballs / bats CoR is limited

when two or more objects come into contact with (exert forces on) each other during a short period of time.

refers to the force acting between two surfaces that are not moving relative to each other

ice skating / skiing - to maximise speed and fluency over ice/snow

Law of inertia - an object at rest stays at rest, and an object in motion stays in motion with the same speed and in the same direction, unless acted upon by an

f = coefficient friction N (or R)

nature of the 2 surfaces in contact with each other - how slippy or rough they are

“A force that acts parallel to the interface of two surfaces that are in contact, and opposes their relative motion”

Static - This explains why it is harder to start moving a heavy sled than to keep it moving.

squash ball warm up - ball travels faster when it is warm