Forces and motion

Mark a line on the ramp to make sure that the car starts from the same point every time you take a measurement
Measure the distance between each light gate using a metre ruler
Let go of the car and let it roll down the slope
Repeat and average the time it takes for the car to travel between the light gates
(Change independent variable)
Repeat the experiment
Using the data find the acceleration: acceleration= change in velocity/ time

(v-u)/t
(final velocity-initial velocity)/time

uphill sections represent acceleration
downhill sections represent decceleration
the steeper the line, the greater the acceleration or the decceleration
Flat sections represent a constant speed
A curve represents changing acceleration or decceleration
Area under any part of the graph is equal to the distance travelled in that time interval

(initial velocity squared) + (2 x acceleration x distance)

Have magnitude but not direction

Have both magnitude and direction

Temperature
Speed
Distance
Time
Weight
Energy
Density
Pressure
Mass

Velocity
Displacement
Acceleration
Acceleration due to gravity

mass x acceleration

push
pull
drag/air resistance
upthrustuoyancy
friction
weight
electrostatic
magnetic
contacteaction
tension
thrust

Force is a vector as it has direction
Therefore we can add forces together, taking into account their direction
We call this resolving the forces to find the resultant force

An object stays at the same velocity if there is no resultant force on it

the bigger the force, the bigger the acceleration
if the force remains fixed, the bigger the mass, the smaller the acceleration
F=ma

For every action, there is an equal and opposite reaction
So if object A exerts a force on object B, then object B exerts a force of the same size on object A but in the opposite direction

Force due to gravity

Resistive force when a surface tries to move across another

Resistive force when an object travels through water

Resistive force when an object travels through air

Upward force on an object, typically in water or air

A force acting in the opposite direction to an action
Most often used as the upward forcewhen a solid object rests on another

Force transmitted through a string, rope, cable or wire when pulled

Force of attraction or repulsion between a magnet and magnetic objects

Forces of attraction or repulsion between two charged objects

When an object first starts to fall, it has much more force (weight) accelerating it than resistance (drag) slowing it down so weight is the resultant force
As velocity increases, the resistance (drag) increases
Eventually the resistance (drag) force is equal to the weight and so there is no acceleration and an object is at terminal velocity

How much an object has a tendency to keep going or how difficult it is to stop it
Vector quantity

mass x velocity

In a closed system (no other forces), the total momentum before the event (collision) is equal to the total momentum after the event
total momentum before = total momentum after

change in momentum/time taken
(mv-mu)/t

When a car crashes, it experiences a large change in momentum
Crumple zones in cars increase the time taken over which a collision occurs
This reduces the decceleration of the car and thus decreases the force experienced by the driver and passengers

When a car crashes, it experiences a large change in momentum
Seatbelt stops you hitting something and increases time for change in momentum to occur
so force is lower and there is less chance of injury

increased time to stop
decreases rate of change of momentum
so reduces force on object

force x perpendicular distance from pivot
M= Fd
Measured in Nm

the clockwise moment equals the anticlockwise moment if an object is balanced

an imaginary point where all the mass of an object can be considered to be concentrated

Suspend the object and a plumb line from the same point and wait until they stop moving
Draw a line along the plumb line
Do the same thing again, but suspend the shape from a different pivot point
The centre of gravity is where your two lines cross