phys Cheat Sheet by userunkn0wn

Accele­ration: The rate of change of velocity.

Braking Distance: The distance travelled between the brakes being applied and the vehicle coming to a stop. It is affected by the vehicle and road condit­ions.

Displa­cem­ent­-Time Graphs: Plots showing how displa­cement changes over a period of time. The gradient gives the velocity. Curved lines represent an accele­ration

Instan­taneous Speed: The exact speed of an object at a specific given point

Reaction Time: The time taken to process a stimulus and trigger a response to it. It is affected by alcohol, drugs and tiredness.

Thinking Distance: The distance travelled in the time it takes for the driver to react. It is affected by alcohol, drugs and tiredness

Velocity: The rate of change of displa­cement. It is a vector quantity and so has both a direction and a magnitude.

Conser­vation of Energy: In a closed system with no external forces the total energy of the system before an event is equal to the total energy of the system after the event. The energy does not need to be in the same form after the event as it was before the event.

Efficiency: The useful output (e.g. power, energy) of a system divided by the total output.

Power: The work done or energy transf­erred by a system divided by the time taken for that to be done.

Conser­vation of Momentum: The total momentum of a system before an event must be equal to the total momentum of the system after the event, assuming no external forces act.

Impulse: The change of momentum of an object when a force acts on it. It is equal to the product of the force acting on the object and the length of time over which it acts.

Linear Momentum: The product of an object’s mass and linear velocity.

Newton’s Second Law: The sum of the forces acting on an object is equal to the rate of change of momentum of the object.

Archim­edes’ Principle: The upwards force acting on an object submerged in a fluid, is equal to the weight of the fluid it displaces.

Centre of Mass: The single point through which all the mass of an object can be said to act.

Density: The mass per unit volume of a material.

Equili­brium: For an object to be equili­brium, both the resultant force and resultant moment acting on the object must be equal to zero

Friction: The resistive force produced when there is relative movement between two surfaces

Newton’s Second Law: The sum of the forces acting on an object is equal to the rate of change of momentum of the object. It is also expressed as the net force acting an object equaling the product of the object’s mass and accele­ration

Pressure: The force that a surface experi­ences per unit area. It is measured in Pascals (Pa)

Tension: The result of two forces acting on an object in opposite, outwards direct­ions.

Triangle of Forces: A method of determ­ining the resultant force of two forces. The two forces are joined tip to tail and the resultant force is given by the force that would complete the triangle

Weight: The product of an object’s mass and the gravit­ational field strength at its location

Brittle: A brittle object is one that shows very little strain before reaching its breaking stress.

Compre­ssive Deform­ation: The changing of an object’s shape due to compre­ssive forces.

Elastic Deform­ation: If a material deforms with elastic behaviour, it will return to its original shape when the deforming forces are removed. The object will not be perman­ently deformed.

Extension: The increase of an object’s length

Hooke’s Law: The extension of an elastic object will be directly propor­tional to the force applied to it up to the object’s limit of propor­tio­nal­itH­ooke’s Law: The extension of an elastic object will be directly propor­tional to the force applied to it up to the object’s limit of propor­tio­nality

Angular Velocity: An object’s rate of change of angular position.

Centri­petal Force: The resultant force respon­sible for an object moving in circular motion. Centri­petal forces always act towards the centre of the object’s rotation.