P2.Forces

• What do scalar quantities have?

  Magnitude only
• What do vector quantities have?

  Magnitude and direction
• How can a vector quantity be represented?

  By an arrow
• What does the length of an arrow in a vector represent?

  The magnitude of the vector
• What does the direction of an arrow in a vector represent?

  The direction of the vector quantity
• What is a force?

  A push or pull on an object
• What are the two types of forces?

  Contact and non-contact forces
• What are examples of contact forces?

  Friction, air resistance, tension
• What are examples of non-contact forces?

  Gravitational force, electrostatic force
• What type of quantity is force?

  A vector quantity
• What is weight?

  The force acting on an object due to gravity
• What causes the force of gravity close to the Earth?

  The gravitational field around the Earth
• What does the weight of an object depend on?

  The gravitational field strength at that point
• How is weight calculated?

  Weight = mass × gravitational field strength
• What is the symbol for weight?

  W
• What is the unit of weight?

  Newtons (N)
• What is the unit of mass?

  Kilograms (kg)
• What is the unit of gravitational field strength?

  Newtons per kilogram (N/kg)
• Where does the weight of an object act?

  At the object's centre of mass
• What is a resultant force?

  A single force replacing multiple forces
• How can the resultant of two forces be calculated?

  By adding or subtracting their magnitudes
• What is a free body diagram used for?

  To illustrate forces acting on an object
• What happens when forces are balanced?

  The resultant force is zero
• What is the moment of a force?

  The turning effect of a force
• How is the moment of a force calculated?

  Moment = force × distance
• What is the unit of moment?

  Newton-metres (Nm)
• What happens when an object is balanced?

  Total clockwise moment equals total anticlockwise moment
• What can levers and gears do?

  Transmit the rotational effects of forces
• What is pressure in a fluid?

  A force normal to any surface
• How is pressure calculated in a fluid?

  Pressure = force / area
• What is the unit of pressure?

  Pascals (Pa)
• What happens to pressure with increasing height in a liquid?

  Pressure increases with height and density
• What creates atmospheric pressure?

  Air molecules colliding with a surface
• How does atmospheric pressure change with altitude?

  It decreases with increasing altitude
• What is distance?

  How far an object moves
• What is displacement?

  Distance in a straight line with direction
• What is speed?

  Distance travelled per unit time
• What factors affect a person's speed?

  Age, terrain, fitness, distance
• What is a typical walking speed?

  Approximately 1.5 m/s
• What is a typical running speed?

  Approximately 3 m/s