Physics - physics and maths tutor

• Speed

  Distance travelled per unit time
• Acceleration

  Change in velocity per unit time
• Velocity

  Speed in a given direction
• Distance-time graph

  Gradient is velocity, Negative gradient is returning to starting point, Horizontal line is stationary, Distance zero is back at starting point, Curved line is accelerating
• Velocity-time graph

  Gradient is acceleration, Negative gradient is deceleration, Speed zero is at rest, Horizontal line is constant speed, Area under line is distance travelled, Curved line is changing acceleration
• Vector

  Has magnitude and direction
• Scalar

  Has just a magnitude
• Examples of Scalars

  • Distance
  • Speed
  • Time
  • Energy
• Examples of Vectors

  • Displacement
  • Velocity
  • Acceleration
  • Force
• Forces

  • Can change speed, shape or direction of a body, Measured in Newtons (N)
• Friction


  Force between two surfaces which impedes motion and results in heating, Air resistance is a form of friction
• Finding resultant of forces

  Add if in same direction, Subtract if in opposite direction
• Newton's first law

  An object has a constant velocity unless acted on by a resultant force
• Newton's third law

  Every action force has an equal and opposite reaction force
• Mass

  Measure of how much matter is in an object, Measured in kilograms (kg)
• Weight

  Gravitational force, Effect of a gravitational field on a mass, Calculated as Mass x Gravitational field strength
• Gravitational field strength on Earth is 10N/kg
• Weight of an object acts through its centre of gravity
• Motion of a body falling in a uniform gravitational field


  1. Initially no air resistance, only weight force

  2. As it falls, speed increases and air resistance increases

  3. Resultant force downwards decreases

  4. Acceleration decreases, not speeding up as quickly

  5. Eventually air resistance and weight balance, terminal velocity reached
• Thinking distance

  Distance travelled between driver realising need to brake and actually pressing brakes, Increased by greater speed, slower reaction time
• Braking distance

  Distance travelled between pressing brakes and vehicle stopping, Increased by greater speed or mass, poor road/car conditions
• Stopping distance

  Sum of thinking distance and braking distance
• Deformation

  Change in size and shape of a body due to a force
• Elastic deformation

  Object returns to original shape when load removed, e.g. stretching a spring
• Force-extension graph

  Linear graph follows Hooke's law, Gradient is spring constant, Non-linear graph does not follow Hooke's law, Fractures after this region
• Moment of a force

  Measure of its turning effect, Calculated as Force x Perpendicular distance from pivot, Measured in Newton metres (Nm)
• Equilibrium

  Sum of clockwise moments equals sum of anticlockwise moments, No resultant force
• Horizontal beam

  Upwards forces at supports change with position of heavy object, Greater force at support nearer heavy object
• Safety features in cars

  Increase time taken for people to come to rest, Reducing force e.g. seatbelt stretching
• Conservation of momentum


  Total momentum before collision equals total momentum after collision