Ch.8 - Force, Mass + Momentum

friction

force that opposes motion

force

causes the velocity of an object to change (causes the object to speed up, slow down or change direction)

SI unit of force, is it vector or scalar

the Newton (N) - vector

what causes acceleration?

force

mass

measure of the amount of matter in a body

SI unit of mass - scalar or vector?

kg - scalar

formula of force

force = mass x acceleration

weight

force of the earth’s gravity acting on an object

formula of weight

weight = mass x accleration due to gravity

momentum formula

p = mass x velocity (p=mv)

SI unit of momentum

kilogram metre per second

newton’s 1st law of motion

a body remains at rest or constant velocity unless acted on by a net external force

newton’s 2nd law of motion

rate of change of a body’s momentum is directly proportional to the net force acting on it and is in the direction of the force

newton’s 3rd law of motion

if a body A exerts a force on body B, then B exerts an equal but opposite force on A

principle of conservation of momentum

in any interaction between 2 or more bodies, the total momentum of the bodies before the interaction is equal to the total momentum after the interaction, provided no external forces act on the system of the bodies

Terminal velocity

1. Weights acts on skydiver, he accelerates down.

2. As he starts to move, air resistance begins to act upwards

3. As speed increases, air resistance increases.

4. Eventually, weight and air resistance are equal and opposite, so the resultant force is 0.

Velocity is now constant = terminal Velocity