Paper 2

• A force is a push or a pull that acts on an object due to the interaction with another object
• Forces are vector quantities because they have both magnitude (size) and direction
• The resultant force is a single force that has the same effect as all of the original forces acting together
• To work out the resultant force, we subtract the smaller force from the larger force
• Newton's First Law of Motion:

  If the resultant force acting on a stationary object is zero, then the object will remain stationary.
• The velocity of an object will only change if a resultant force is acting on the object
• A resultant force causes an object's speed to change
• If a stationary object experiences a resultant force of zero, then it will remain stationary
• If a moving object experiences a resultant force of zero, it will continue moving at the same speed and in the same direction
•  a resultant force which is not zero will cause an object's velocity to change
• Newton's Second Law of Motion:

  The acceleration of an object is proportional to the resultant force acting on the object, and inversely proportional to the mass of the object.
• If we have a greater force, then we have a greater acceleration
• If the mass is larger then the acceleration will be smaller
• Force (N) = Mass (kg) x Acceleration (m/s2)
• Inertia

  An object will stay stationary, or continue moving at the same speed and direction, unless a resultant force is applied.
• Whenever two objects interact, the forces they exert on each other are equal and opposite
• This force is equal in magnitude but opposite in direction.
• newton’s third law is When two objects interact, the forces they exert on each other are equal and opposite
• newton’s first law is If the resultant force on a stationary object is zero, the object will remain stationary. If the resultant force on a moving object is zero, it'll just carry on moving at the same velocity
• waves transfer energy from one place to another without transferring matter
• for waves in water and air it is the energy not the substance that moves
• mechanical waves require a substance to travel through
• examples of mechanical waves:

  • sound waves
  • water waves
  • waves on springs and ropes
• the oscillations of a transverse wave are perpendicular to the direction in which the waves transfer energy
• ripples on the surface of water are an example of transverse waves
• the oscillations of a longitudinal wave are parallel to the direction in which the waves transfer energy
• longitudinal waves cause particles in a substance to be squashed closer together and pulled further apart
• sound waves in air are an example of longitudinal waves
• when waves travel from one medium to another, there speed and wavelength may change but the frequency always stays the same
• amplitude (m) maximum displacement of a point on a wave from its undisturbed position
• frequency (Hz) number of waves passing a fixed point per second
• period (s) time taken for one complete wave to pass a fixed point
• wavelength (m) distance from one point in a wave to the equivilent point on the next wave
• wave speed (m/s) distance travelled by each wave per second and the speed at which energy is transferred by the wave
• waves may be transverse or longitudinal
• EM waves

  • Wide range of frequencies can be absorbed or produced by changes inside an atom or nucleus
  • Gamma rays are produced by changes in the nucleus of an atom
• Emission of EM waves

  Electrons in an atom move down between energy levels
• Radio waves

  Produced by oscillations in an electrical circuit
• Radio waves are absorbed by a receiver aerial


  They may create an alternating current with the same frequency as the radio waves
• EM waves

  • Have many practical applications
  • Exposure to some EM waves (such as ionising radiation) can have hazardous effects