Physics P2

• What do scalar quantities have?

  magnitude only
• what do vector quantities have?

  magnitude and an associated direction
• how may a vector quantity be represented?

  by an arrow. the length of the arrow represents the magnitude, and the direction of the arrow represents the direction of the vector quantity
• what is a force?

  a force is a push or pull that acts on a object due to the interaction with another object. all forces between objects are either contact forces or non-contact forces
• what is a contact force?

  the objects are physically touching
• what is a non-contact force?

  the objects are physically separated
• what are examples of contact forces?

  friction, air resistance, tension and normal contact force
• what is examples of non-contact force?

  Gravitational forces, magnetic force and electrostatic force.
• is force a scalar quantity or vector quantity?

  vector quantity
• what is weight?

  the force acting on an object due to gravity. the force of gravity close to the Earth is due to the gravitational field around the Earth
• what does the weight on an object dependent on?

  it depends on the gravitational field strength at the point where the object is
• how can weight be calculated?

  W = m x g

  weight = N ( newtons )

  mass = kg

  gravitational field strength = N/kg
• what is an objects centre of mass?

  when the weight of an object may be considered to act at a single point
• relationship between the weight of an object and the mass of the object?

  the weight of an object and the mass of an object is directly proportional
• how is weight measured?

  using a calibrated spring-balance ( a newtonmeter )
• what is a resultant force?

  a number of forces acting on an object may be replaced by a single force that has the same effect as all the original forces acting together. this single force is called the resultant force
• how to calculate the resultant of two forces that act in a straight line?

  Vector addition
• describe examples of the forces acting on an isolated object or system?

  Gravity, friction, tension, normal force, air resistance.
• what can a single force be revolved into?

  A single force can be resolved into two components acting at right angles to each other . the two component forces together have the same effect as the single force
• What does a force do on an object?

  when a force causes an object to move through a distance work is done on the object. So a force does work on an object when the force causes a displacement of the object.
• how can the work done by a force be calculated?


  W = F x d

  work done = force x distance

  work done = J ( joules )

  force = N ( newtons )

  distance = m ( metres )
• work done?

  one joule of work is done when a force of one newton causes a displacement of one meter
• what does 1 joule equal to?

  1 joule = 1 newton-meter
• conversion between joules and newton-meter?

  Equivalent
• what does work done against a frictional force acting on an object cause?

  a rise in the temperature of the object
• what are examples of forces involved in stretching, bending or compressing an object?

  pulling and pushing ?
• why to change the shape of an object more than one force has to be applied?

  a single force will only cause the object to move in the direction in which the forces were applied
• what is the difference between elastic deformation and inelastic deformation caused by stretching forces?

  Elastic deformation is reversible and the material returns to its original shape after the force is removed, while inelastic deformation is permanent and the material does not return to its original shape.
• relationship between the extension of an elastic object and the force applied?

  the extension of an elastic object, such as a spring, is directly proportional to the force applied, provided that the limit of proportionality is not exceeded
• how to calculate force?

  force = spring constant x extension

  F = k x e

  force = N ( newtons )

  spring constant = N/m

  extension = m ( metres )
• what does a force that stretches ( or compresses ) what does a spring do?

  a force that stretches ( or compresses ) a spring does work and elastic potential energy is stored in the spring. provided the spring is not inelastically deformed, the work done on the spring and the elastic potential energy stored are equal.
• what is the difference between a linear and non-linear relationship between force and extension?

  Linear relationship: Force and extension have a constant ratio and graph a straight line. Non-linear relationship: Force and extension do not have a constant ratio and graph a curve.
• how to calculate elastic potential energy?

  Ee = 1/2 x k x e^2
• force and extension PRACTICAL?

  measure natural length of spring ( when no load is applied ) with a mm ruler clamped to the stand. Make sure you take reading at eye level and add a marker ( eg thin strip of tape ) to the bottom of spring to make reading more accurate. Add mass to spring and allow it to come to rest. Record mass and measure new length of the spring. The extension is the change in length. Repeat this process until you have enough measurements ( no fewer than 6 ). Plot a force ( x ) - extension ( y ) of your results. It will only curve if you exceed the limit of proportionality.
• what is distance and what does it involve?

  distance is how far an object moves. distance does not involve direction. distance is a scalar quantity.
• what does displacement include and what is it?

  both the distance an object moves, measured in a straight line from the start point to the finish point and the direction of that straight line. displacement is a vector quantity
• what is speed and what doesnt it involve?

  speed doesnt involve direction. its a scalar quantity
• why is speed rarely constant?

  the speed of a moving object is rarely constant. when people walk, run or travel in a car their speed is constantly changing
• what does speed at which a person can walk, run or cycle depend on?

  factors : age, terrain, fitness and distance travelled
• what are the typical values of walking, running and cycling?

  walking -> 1.5 m/s

  running -> 3 m/s

  cycling -> 6 m/s