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Independent variable, Dependant variable and control variable
Independent variable = the thing you change in an investigation, dependant variable = the thing you measure in an investigation, control variables = anything you keep constant in an investigation.
Resolution
The resolution of a piece of equipment is the smallest value the equipment can read to e.g. a ruler can read to 1mm
Uncertainty in means
The uncertainty in a mean result gives you the range of values that you expect the true value to lie between.
How to find uncertainty
To find uncertainty, you need to repeat your investigation. Uncertainty = ½ range of your repeated results
reason for repeating results
to look for anomalies and reduce the impact of random errors
Dataloggers attached to probes are better than normal lab equipment because:
The resolution is better, It reduces the chance of human error, You can take many results in quick succession and You can take results over a long period of time e.g. over night
Scalar and vector quantities
A scalar quantity has a magnitude (size) only, a vector quantity has a magnitude and direction.
Scalar examples
Distance travelled, speed, mass, time, energy
Vector examples
Displacement, velocity, any force, acceleration, Momentum
Contact and non contact forces
Contact forces: friction, normal contact force, air resistance and tension. Non-contact forces: weight/gravitational force, magnetic force, electrostatic force between charged particles.
Weight definition
Weight is the force acting on an object due to gravity. DO NOT CALL IT GRAVITY. It depends on the gravitational field strength and mass of the object and acts from the “centre of mass”
Newtons First Law
An object will remain at rest, or in constant motion, unless acted upon by a resultant force
Inertia
The tendency of objects to continue in their state of rest or of uniform motion
Newtons Second Law
acceleration is directly proportional to resultant force and inversely proportional to mas
Inertial mass
a measure of how difficult it is to change the velocity of an object, it is defined as the ratio of force over acceleration
Newtons Third Law
If object A puts a force on object B, object B will put an equal and opposite force on object A.
Stretching an object
If you want to stretch, bend or squash an object, you need more than one force (one to hold it in place), otherwise the object will just accelerate; stretching an object stores elastic potential energy.
Stretching force
The stretching force applied to an object is directly proportional to the extension
Elastic and inelastic materials
Elastic materials will return to their original shape after the deforming force is removed, inelastic materials will not (they are permanently deformed)
Distance and Displacement
Distance (scalar) is how far an object moves, displacement (vector) is how far an object moves overall from start to finish in a straight line with the direction
Speed and Velocity
Speed (scalar) is how fast an object is going, velocity (vector) is the speed with direction.
Typical speeds
Walking - 1.5m/s, Running – 3m/s, Cycling – 6m/s, Sound in air – 330m/s
The gradient of a distance-time graph
Speed
The gradient of a velocity-time graph + the area under it
The gradient of a velocity-time graph is the acceleration, the area under the graph is the distance travelled.
A system
a group of objects that interact.
Energy stores
Kinetic, Gravitational potential, Elastic potential, Nuclear, Chemical, Internal (sometimes called Thermal), Magnetic
Energy transfers
Via Heat (radiation), Via Sound (radiation), Via Light (radiation), Electrically, Mechanically (by forces)
Conservation of energy
The total energy of a system remains constant so energy cannot be created or destroyed; it can only be transferred between stores.
Efficiency
a measurement of how much useful energy comes out of a device, compared to how much energy went in
Energy unit
Energy is measured in Joules (J)
Note 
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