Physics

Vectors - Have direction:   -------------

Scalars - Don't:   

Vectors: Displacement, Velocity, Weight (Most Forces)

Scalars: Distance, Speed, Energy, Time

Displacement - Distance covered in a straight line

Velocity can change even if the speed doesn't because the direction is changing

Speed = Distance / Time

Average Speed = Distance Travelled / Time Taken

Instantanious Speed - Speed at a particular point in a journey

Distance = Speed x Time 

Example:

Car travelled 3000m in 2mins (120 secs)

3000 / 120 = 25 mph

Velocity - The rate at which an object changes position

Velocity = Distance (Displacement) / Time

Area:

1 - AOT - Area of triangle ((base x height)/2)

2 - AOR - Area of rectangle (width x height)

3 - Area under Graph (AOT + AOR)

Area under graph gives distance travelled

Gradient : 

Change in Y / Change in X

The gradient of the line gives the acceleration 

'an object at rest stays at rest'

'an object in motion stays in motion'

_____O_____ - There are no unbalanced forces so this will not move

----> O ----> - The forces are balanced so this will not stop

Centripetal force - a force that causes objects to follow a circular path

-  the force acts toward the centre of the circle 

- friction and gravity can be centripetal forces 

- an object moving in a circle has a changing velocity but its speed remains the same

Mass - amount of matter in an object

mass = weight / gravitational feild strength 

Weight is a force

weight = mass x gravitational feild strength 

! On earth, the GFS is ALWAYS 10!

Acceleration - Change in velocity in a ceratin time 

acceleration = change in velocity / time taken

Acceleration is a vector quantity

Deceleration - Slow down

force = mass x acceleration 

'For every action there is an equal and opposite reaction'

----> <----

momentum = mass x velocity

Momentum is a vector quantity 

Conservation of linear movement:

'If a moving object collides with another object, the total momentum of the two objects before the collision is the same during the collision'

stopping distance = thinking distance + braking distance of a vehicle 

The thinking distance: distance travelled by vehicle whilst driver is reacting

- This can be affected by drugs, alchohol, tiredness 

Average human reaction time = 0.25 seconds

The breaking distance: distance car travels after the driver has started breaking

- Can be affected by road conditions (icy, wet) and by faulty brakes or tyres

Crumple zones and airbags :

- Slow down the rate of change in momentum for both the car and passenger

- A slower change in momentum means less force is applied at any one time

- The passengers survive the lower force even though they are applied for longer

Crumple zone:

- The car does not need as much deceleration to come to a stop so the force acting on it is less

Seatbelt:

- Holds you in your seat so you slow down at the same rate as the car

If forces are acting in the same direction --> --> then add them

If forces are acting in opposite directions --> <-- then subtract the larger force from the smaller one