Physics

• Distance


  How far two points are apart
• Displacement


  Measures the distance apart between two points and specifies their direction
• Speed


  The rate at which distance travelled changes with time
• Velocity


  The rate of change of displacement with time
• Average speed


  Total distance travelled divided by total time taken
• Average velocity


  Total displacement divided by total time taken
• Rate of change of speed


  Final speed - initial speed divided by time taken
• Rate of change of speed

  Measured in metres per second squared
• Rate of change of speed has no direction since speed has no direction
• Calculating average speed when rate of change of speed is constant


  Initial speed + final speed divided by two
• Acceleration


  The rate of change of velocity with time
• Scalar


  A physical quantity that has magnitude but not direction
• Vector


  A physical quantity that has both magnitude and direction
• Gradient of a distance-time graph


  Represents an object's speed
• Gradient of a speed-time graph


  Represents an object's rate of change of speed
• Area between a speed-time graph and the time axis


  Represents the distance moved
• Gradient of a displacement-time graph

  Represents an object's velocity
• Gradient of a velocity-time graph

  Represents an object's acceleration
• Area between a velocity-time graph and the time axis

  Represents the displacement
• Balanced forces


  When there is no resultant force on an object
• Unbalanced forces


  When there is a resultant force causing an acceleration
• Mass


  Measured in kg and shows the amount of matter in an object
• Weight


  The force of gravity on an object
• Acceleration of free fall

  The acceleration of an object toward the surface of the earth when the only force on it is the gravitational force
• Gravitational field strength


  The gravitational force in an object of mass one kilogram close to the surface of a planet
• Hooke's law


  The extension is directly proportional to the applied load, up to a limit known as the limit of proportionality
• Natural length


  The length of a spring when no stretching or compressing forces are applied
• Extension


  The difference between the stretched length of a spring and its natural length
• Centre of gravity


  The point through which the entire weight of a body appears to act
• Equilibrium


  A state in which opposing forces or moments are balanced
• Neutral equilibrium


  A state in which slight displacement causes the object neither to move very far from its original position
• Stable equilibrium


  A state in which slight displacement causes the object to return to its original position
• Moment about a point

  The product of a force and its perpendicular distance from the point
• The principle of moments states that when a lever is balanced, the sum of the clockwise moments about any point equals the sum of the anticlockwise moments about the same point
• Density


  The mass of an object divided by its volume
• Kinetic theory


  Explains the properties of solids, liquids and gases according to the arrangement and motion of their molecules