Action: A force being applied.

Bounce: To reverse direction (and velocity) on impact.

Collision: An occurrence in which two or more objects exert forces on each other.

Coefficient of friction: For a particular pair of surfaces, the coefficient of friction is the ratio of the sliding force over the force acting perpendicular to the surfaces in contact.

Fluid: A material that can flow: usually a liquid or a gas.

Friction: The force that resists or tends to resist relative motion of surfaces, materials or particles in contact with each other.

Static friction: A certain force is needed to initiate relative motion between surfaces or parts of a material. The force that opposes initial movement is called static friction.

Dynamic friction: Less force is usually needed to maintain relative movement than to initiate movement. The force that opposes constant relative movement between surfaces or parts of a material is known as the dynamic friction.

Interaction: A mutual action between objects.

Momentum: The product of mass and velocity

Impulse: The product of force and time.

Projectile: An object that is given an initial velocity and then moves only under the influence of gravity.

Resultant: The combined effect of two or more vectors.

Reaction: The equal and opposite force to the force being applied.

Trajectory: The path followed by a projectile.

Velocity Component: A portion of the velocity of an object that acts in a given direction.

Viscosity: An indicator of the tendency to oppose relative motion of the particles/molecules that make up a fluid. The greater the viscosity the slower the fluid tends to flow under the influence of a specific force.

Vector: A line, arrow or set of coordinates that represents a quantity and its direction.

............................................... Friction force
Coefficient of friction = ---------------------------
......................................... Force between surfaces

v = at

Velocity = acceleration x time

Where: v = velocity

a = acceleration (M/s²)

t = time (s)

d = vt

Distance = velocity x time

Where: d = distance (m)

v = velocity^* (m/s)

t = time (s)

(*If v changes with time, use average velocity)

d = ½at²

Distance = ½ x acceleration x time² (for accelerating object)

Where: d = distance (m)

a = acceleration (m/s²)

t = time (s)

a_c = v ²/r

Centripetal acceleration = (tangential velocity)² ÷ radius of curve

Where: a_c = centripetal acceleration (m/s²)

v = tangential velocity (m/s)

r = radius of curve (m)

For a projectile launched vertically from the ground at a velocity = v₀ :

v = v₀ - gt

Velocity = initial upward velocity – (acceleration due to gravity x time)

Where: v = velocity (m/s)

v₀ = initial velocity (m/s)

g = acceleration due to gravity (9.81 m/s²)

t = time (s)

t_max = v₀ /g

Time to reach maximum height = initial velocity ÷ acceleration due to gravity

Where: v₀ = initial velocity (m/s)

g = acceleration due to gravity (9.81 m/s²)

t_max = time to reach maximum height (s)

d_max = ½g t_max ²

Maximum height = ½ x acceleration due to gravity x time²

Where: d_max = maximum height (m)

g = acceleration due to gravity (9.81 m/s²)

t_max = time to reach maximum height (s)

d_max = [(v₀ + v_t)/2] t_max

Maximum height = average velocity x time

Where: d_max = maximum height (m)

v₀ = initial velocity (m/s)

v_t = velocity at max height = 0 (m/s)

t_max = time to reach maximum height (s)

Momentum = mv

Momentum = mass x velocity

Impulse = ft

Impulse = force x time

Impulse = D (mv)

Impulse = change in momentum

F = ma

Force = mass x acceleration

Where: F = force (N)

m = mass (kg)

a = acceleration