WHOLE OF PHYS PAPER 2

• Vector quantities


  have magnitude and direction
• Examples of vector quantities

  force, velocity, momentum, acceleration
• Scalar quantities


  Only have magnitude and no direction
• Examples of scalar quantities


  speed, distance, time
• Vectors


  represented by an arrow - the length of the arrow shows the magnitude. The direction of the arrow shows the direction of the quantity
• A force is


  a push or pull on an object that is caused by it interacting with something
• when two objects are touching for the force to act, its a ....

  contact force
• examples of contact forces


  friction, air resistance, tension in ropes. etc
• If the objects do not need to be touching for the force to act, the force is a ......

  non contact force
• examples of non contact forces

  magnetic force and gravitational force
• Two effects of gravity

  - makes all things fall towards the ground

  - gives everything a weight
• What is mass?


  The amount of material an object is made of

  It is the same value everywhere

  Measured using a mass balance
• What is weight?


  The force acting on an object due to gravity

  It depends on the strength of the gravitational field at the location of the object

  Measured using a calibrated spring balance - newtonmeter
• Equation for Weight


  Weight (N) = Mass (kg) x Gravitational Field Strength (N/kg)

  W=mg
• What is weight directly proportional to?

  mass
• What are free body diagrams?

  Diagrams that show all the forces acting on an object

  
• What is the resultant force?

  The single force that replaces multiple forces acting at a single point
• How is work done?

  When a force moves an object through a distance, energy is transferred and work is done on the object
• Equation for 'Work Done'

  Work done (J) = Force (N) x Distance (m)

  W=Fs
• What is 1J equal to?

  1Nm
• If all the forces acting on an object combine to give a resultant force of zero then the object is in ?

  equilibrium
• What could happen when you apply a force to an object?

  It may stretch, compress or bend
• What happens when an object is elastically deformed


  The object can go back to its original shape and length after the force has been removed
• What happens when an object is inelastically deformed?


  The object won't return to its original shape and length after the force has been removed
• Equation for Force 1

  Force (N) = Spring Constant (N/m) x Extension (m)

  F=ke
• Extension is directly proportional to? (Hooke's Law)

  The force applied

  F∝e
• What is the limit of proportionality?


  The point at which extension is no longer directly proportional to force

  
• Practical: Investigating the link between force and extension

  - First, measure the original length of the spring using a milimetre ruler

  - Next, add different masses on the spring and measure the length of the spring in each case.

  - The extension = change in length

  - Repeat this process until you have enough measurements ( no fewer than 6)

  - Plot a graph with extension of the spring on the x axis and force on the y axis.

  - The graph will only start to curve if you exceed the limit of proportionality
• Equation for Elastic potential energy

  Elastic potential energy (J) = 1/2 x Spring Constant (N/m) x extension^2 (m)

  Ee = 1/2Ke^2
• What is displacement?


  It measures the distance and direction in a straight line from an object's starting point to its finishing point
• What is velocity?


  Speed (how fast you're going) in a given direction
• Equation for Speed


  Distance Travelled (m) = Speed (m/s) x Time (s)

  s=vt
• typical speeds


  typical speed of a person walking

  1.5m/s

  typical speed of a person running

  3m/s

  Typical speed of a person cycling

  6m/s

  what is the typical speed of a car

  25m/s

  Typical speed of a train

  55m/s

  Typical speed of a plane

  250m/s
• What factors affect speed?

  Fitness of the person

  Age of the person

  Distance travelled

  Terrain

  Climate

  Gender of the person
• What factors affect wind speed?

  Temperature

  Atmospheric pressure

  Any large buildings or structures nearby e.g. forests reduce wind speed travelling through them
• Acceleration


  change in velocity in a certain amount of time
• Equation for Acceleration


  Acceleration (m/s²) = Change in Velocity (m/s) / Time (s)

  a=Δv/t
• What is deceleration?


  Negative acceleration - when something slows down, the change in velocity is negative
• What is constant acceleration?

  Uniform acceleration - acceleration due to gravity is uniform for objects in free fall
• Equation for Uniform Acceleration

  Final velocity² (m/s) - Initial velocity² (m/s) = 2 x Acceleration (m/s²) x Distance (m)

  v²-u²=2as