force

scalar quantities and examples

• magnitude (size)

• eg = speed, distance, mass energy, temp, time

vector quantities and examples

• both magnitude and direction

• eg = velocity, displacement, force, weight, acceleration, momentum

vector diagrams

• length of arrow = magnitude

• direction of arrow point = quantity

contact forces

• friction

• air resistance

• tension

• normal contact force

non contact forces

• gravitational force

• electrostatic force

• magnetic force

difference between mass and weight

• mass = measured in kg and universally same

• weight = force acting on an object due to gravity and measured in newtons

key concepts for gravity

• weight and mass and directly proportional

• weight acts at a single point in an object called the centre of mass

if resultant force is 0?

• objects motion doesnt change

• stays still or keeps moving in the same velocity

if there’s a resultant force?

• object accelerates in the direction of that force

elastic deformation

• object returns to its original shape when the force is removed

inelastic defomation

• object stays stretched and doesn’t return to its original shape

limit of proportionality

the bending of line in a force-extention graph

flat line in DT graphs

• object is stationary

straight uphill line in DT graphs

• constant speed

gradient in DT graphs

• speed

newtons first law

if a resultant force is 0:

• stationary object stays stationary

• moving object continues to move in same velocity

newtons second law

acceleration of an object is proportional to the resultant force

and inversely proportional to mass

terminal velocity

• initially = only force is weight downwards. object accelerates downwards

• as speed increases = air resistance increases upwards

• this reduces resultant force so acceleration increases

• eventually = air resistance equals weight. Resultant force is 0

• result = object reaches terminal velocity

thinking distance affects

• tiredness

• drugs

• alcohol

• distractions

braking distance affects

• icy roads

• worn tired

• work brakes

• speed

conservation of momentum

• in a closed system = total momentum before is equal to total momentum after event

walking speed

1.5 m/s

running speed

3 m/s

cycling speed

6 m/s

speed of sound in air

330 m/s

gradient in VT graphs

acceleration

flat line in VT graphs

constant velocity

area under VT graph

Distance travelled

stopping distance?

thinking distance + braking distance

if speed doubles, what happens to

thinking distance?

braking distance?

• thinking distance = doubles

• braking distance = quadruples

conservation of momentum?

in a closed system = total momentum before an event is equal to total momentum after event