Physics 2

• Scalar quantities


  Only have magnitude
• Vector quantities


  Have magnitude and direction (represented with arrows)
• Force


  Push or pull that acts on an object due to an interaction with another object
• Contact force


  Objects are physically touching
• Examples of contact forces


  Friction, air resistance, tension and normal contact force
• Non-contact force


  The objects are physically separated
• Examples of non-contact forces

  Gravitational, electrostatic and magnetic force
• Weight


  Force acting on an object due to force. It depends on the gravitational field strength
• Unit for weight


  Newtons (N)
• Unit for mass


  Kilogram (kg)
• Unit for gravitational field strength


  Newtons per kilogram (N/kg)
• Resultant force


  An overall force on an object that takes into account all the forces acting on an object in different directions
• If there is a resultant force acting on an object what does that mean?

  Object is accelerating or decelerating
• If there is no resultant force on an object what does that mean?

  Object is moving at a constant speed or is stationary
• Work done


  Energy transferred
• Conversion of Joules to Newton-metres

  1 Joule = 1 Newton-metre
• Why is there forces acting in at least 2 directions when changing the shape of an object (stretching, compressing etc) ?

  As the ball remains stationary so the resultant force is zero
• Elastic deformation


  Region where the material will return to its original shape when the stress is removed
• Plastic deformation


  Permanent deformation caused by strain when stress exceeds a certain value
• Displacement


  How far an object is away from where it started (+ or -)
• Distance


  How far an object has travelled
• Speed


  The distance an object travels per unit of time
• Velocity


  Speed in a given direction
• Speed of sound


  33 m/s
• On a displacement time graph...

  What is represented by the gradient of the line?

  The velocity
• On a velocity time graph...

  What is represented by the gradient of the line?

  Acceleration
• On a displacement time graph...

  What does a straight line mean about the motion of the object


  Constant speed (could be zero if horizontal)
• On a velocity time graph...

  What does a straight line mean about the motion of the object?

  Constant acceleration (could be zero acceleration if horizontal)
• How do you calculate gradient of a straight line?

  Difference between y-coordinates/difference between x-coordinates

  
• On a displacement time graph...

  What does it mean if there is negative gradient? (the line slopes downwards)


  The object is moving back towards its starting position
• If an object is falling on Earth near the surface what is its acceleration?

  9.8 m/s^2
• Newton's first law:

  If a stationary object has a resultant force of zero what will happen to it?


  It will stay stationary
• Newton's first law:

  If a moving object has a resultant force of zero what will happen to it?

  Stay moving with same velocity
• Stopping distance


  Thinking distance + braking distance
• Factors affecting reaction time

  Tiredness, drugs, alcohol, distractions
• Factors affecting braking distance

  Road condition, tyre condition, weather
• Dangers of large decelerations

  Large braking force so brakes overheating and loss of control
• Conservation of momentum


  Total momentum before the event is equal to total momentum after the event (in a closed system)
• Transverse waves


  A wave vibrating at right angles to the direction the wave is travelling

  
• Longitudinal waves


  A wave vibrating parallel to the direction the wave is travelling