definitions

• What is acceleration?

  The rate of change of velocity.
• How is average speed calculated?

  Distance over time for the entire region of interest.
• What factors affect braking distance?

  Vehicle and road conditions.
• What is displacement?

  The direct distance between an object’s starting and ending positions.
• What is braking distance?

  The distance traveled between the brakes being applied and the vehicle coming to a stop.
• Why is displacement considered a vector quantity?

  It has both a direction and a magnitude.
• What do displacement-time graphs represent?

  How displacement changes over a period of time.
• What does the gradient of a displacement-time graph indicate?

  The velocity of the object.
• What do curved lines on a displacement-time graph represent?

  An acceleration of the object.
• What is free-fall?

  An object is in free fall when the only force acting on it is gravity.
• What is instantaneous speed?

  The exact speed of an object at a specific point.
• What is projectile motion?

  The motion of an object fired from a point where only gravity acts on it.
• What is reaction time?

  The time taken to process a stimulus and trigger a response.
• How can projectile motion problems be simplified?

  By splitting the motion into horizontal and vertical components.
• What factors affect reaction time?

  Alcohol, drugs, and tiredness.
• What is stopping distance?

  The sum of thinking distance and braking distance for a driven vehicle.
• What is thinking distance?

  The distance traveled in the time it takes for the driver to react.
• What factors affect thinking distance?

  Alcohol, drugs, and tiredness.
• What do velocity-time graphs represent?

  How velocity changes over a period of time.
• What does the gradient of a velocity-time graph indicate?

  The acceleration of the object.
• What do curved lines on a velocity-time graph represent?

  Changing acceleration of the object.
• What is velocity?

  The rate of change of displacement.
• Why is velocity considered a vector quantity?

  It has both a direction and a magnitude.
• What is Archimedes’ Principle?

  The upwards force on an object submerged in a fluid equals the weight of the fluid it displaces.
• What is the centre of gravity?

  The single point through which the object’s weight can be said to act.
• What is the centre of mass?

  The single point through which all the mass of an object can be said to act.
• What is a couple in physics?

  Two equal and opposite parallel forces acting on an object through different lines of action.
• What is density?

  The mass per unit volume of a material.
• What is drag?

  The frictional force experienced by an object moving through a fluid.
• What is equilibrium in physics?

  Both the resultant force and resultant moment acting on the object must be equal to zero.
• What is a free-body diagram?

  A diagram showing all the forces acting on an object.
• What is friction?

  The resistive force produced when there is relative movement between two surfaces.
• What is the moment of force?

  The product of a force and the perpendicular distance from the line of action of the force to the pivot.
• What is the unit of force?

  Newton.
• What does Newton’s Second Law state?

  The sum of the forces acting on an object is equal to the rate of change of momentum of the object.
• What is the normal contact force?

  The reaction force between an object and a surface.
• What is pressure?

  The force that a surface experiences per unit area.
• What is the principle of moments?

  The sum of the clockwise moments must equal the sum of the anticlockwise moments for equilibrium.
• What is tension in physics?

  The result of two forces acting on an object in opposite, outwards directions.
• What is terminal velocity?

  The maximum velocity of an object when resistive and driving forces are equal.