Forces

• Define 'scalar quantity'

  Scalar quantities have magnitude (size) only
• Define 'vector quantity'

  Vector quantities have both magnitude (size) and direction
• What is a force?

  A push or pull
• Define 'contact forces'

  Forces that can only act when objects are touching
• Define 'non-contact forces'

  Forces that can act even when objects are not touching
• State four examples of contact forces

  • friction
  • air resistance
  • tension
  • normal contact force
• State three examples of non-contact forces

  • gravitational force
  • electrostatic force
  • magnetic force
• What is weight?

  The force acting on an object due to gravity pulling on its mass
• What is mass?

  The amount of matter an object contains
• The equation linking weight, mass and gravitational field strength

  weight = mass x gravitational field strength
• What is the equipment used to measure weight?

  A Newtonmeter
• Where does the weight of any object act from?

  The centre of mass
• Define 'resultant force'

  A single force found by adding up all of the individual forces acting on an object
• How do you calculate a resultant force?

  Subtract forces acting in the opposite direction and add forces acting in the same direction
• When is work done on an object?

  When a force moves it a distance in the direction of that force
• The equation linking work done, force and displacement

  work done = force x displacement
• How many Joules is in one Newton-metre?

  1 Joule
• What happens to the temperature of an object when work is doen against friction?

  It increases
• What happens to an elastic object up to the limit of proportionality?

  Elastic deformation (it is able to return to its original length)
• What happens to an elastic object after the limit of proportionality?

  Inelastic deformation (it will not return to its original length)
• What is the relationship between force and extension fro an elastic object?

  They are directly proportional
• The equation linking force, spring constant and extension

  force = spring constant x extension
• Define 'spring constant'

  The stiffness of the spring
• Is distance a scalar or vector quantity?

  Scalar
• Is displacement a scalar or vector quantity?

  Vector
• Is speed a scalar or vector quantity?

  Scalar
• is velocity a scalar or vector quantity?

  Vector
• What is displacement?

  A distance with direction
• What is the typical value of walking speed?

  1.5 m/s
• What is the typical value of running speed?

  3 m/s
• What is the typical value of cycling speed?

  6 m/s
• The equation linking distance, velocity and time

  distance = speed x time
• When moving in a circle at constant speed, why is velocity constantly changing?

  Although the speed remains constant, direction changes and since velocity is a vector quantity, velocity changes
• How do you calculate the speed of an object from a distance-time graph?

  By calculating the gradient
• How do you calculate the distance travelled from a velocity-time graph?

  Calculate the area under the curve/line of the selected time
• How do you calculate acceleration from a velocity-time graph?

  By calculating the gradient
• What is acceleration?

  The change in velocity over a given period of time
• The equation linking acceleration, change in velocity and time

  acceleration = change in velocity / time
• If an object is falling due to gravity on Earth, what acceleration does it have?

  9.8 m/s2
• What is the name of the constant speed a falling object reaches when the resistive force is equal to its weight?

  Terminal velocity