Unit 2 - Motion

distance

scalar quantity measuring the length between objects or points regardless of direction. unit: m, symbol: d

displacement

vector quantity measuring the length between an object’s starting and ending positions with regard to direction. symbol: s, unit: meter (m)

speed

rate at which distance is covered without direction. scalar quantity. symbol: v, unit: m/s

velocity

rate of change in displacement with direction considered. it is a vector quantity. unit: m/s

acceleration

rate of change of velocity. vector quantity. unit: m/s²

vector

quantity that has both magnitude and direction

scalar

quantity that only has magnitude

formula for speed

average speed = total distance / total time

formula for average velocity

average velocity = total displacement / total time

suvat equations

a = (v-u)/t

s = (u+v)/2 - t

s = ut + 1/2at²

v² = u² + 2as

what does gradient of distance-time graph represent

average speed

what does gradient of velocity-time graph represent

acceleration

what does horizontal line on distance-time graph indicate

object at rest

how does speed-time graph differ from velocity-time grpah

velocity time graph can have negative velocity

what does the area under a velocity-time graph represnt

displacement

area under speed-time graph

total distance

force

push or pull on an object resulting from its action with another object causing changes in motion or shape. newtons

2 types of forces

contact forces, field forces

contact force

any force that occurs as a result of two objects making contact with each other

types of contact force

muscular force, tension, air resistance, normal force, frictional

muscular force

Force that is exerted by the weight of muscles.

friction

Friction is the force resisting the relative motion between two surfaces or materials in contact, always acting opposite to the direction of motion. 

tension

A tension force is a force that develops in a rope, thread, or cable as it is stretched under an applied force. 

air resistance

Air resistance is a force that is caused by air. The force acts in the opposite direction to an object moving through the air.

Normal Force

Normal force is a force perpendicular to the surface and equal in magnitude to the amount of weight acting perpendicularly to that surface.

non-contact force

These forces do not need contact to be applied or occur

types of non-contact force

gravitational, electrostatic, magnetic

- Electrostatic:

The electrostatic force is an attractive and repulsive force between particles caused to their electric charges

. - Magnetic:

Magnetic force is the attraction or repulsion between moving electric charges

what is weight

force of gravity acting on mass

weight formula

mass x gravitational acceleration

strength of gravity

10 m/s²

friction formula

F​=μ×N

friction = friction coefficient x normal force

what is stopping distance

Stopping distance is the total distance a vehicle travels from the moment the driver spots a hazard to when the vehicle fully stops.

Stopping Distance=Thinking Distance+Braking Distance

thinking distance

The distance travelled while the driver reacts.

Braking Distance

The distance travelled from pressing the brakes to stopping.

factors affecting thinking distance

• Distractions (phone, passengers, loud music)

• Tiredness / fatigue

• Alcohol or drugs

• Age (younger drivers usually react faster)

• Poor visibility (night, fog)

factors affecting braking distance

Car's condition, road's condition, speed, mass

types of friction

static, sliding, rolling, fluid

static friction

friction preventing surfaces from moving past each other

sliding friction

resistance between two sliding objects

rolling friction

resistance when an object rolls

fluid friction

resistance moving through a fluid