Newtons laws

• Define ‘Terminal velocity’

  The maximum speed of an object reached when the forces moving the object are balanced by its frictional forces
• At terminal velocity the object moves at a..

  Steady speed in a constant direction because the resultant force acting on it is zero
• State the three stages of an object falling:

  The object first accelerates downwards due to the force of gravity

  As the objects speed increases, frictional forces such as drag or air resistance increases

  At terminal velocity, the weight of the object due to gravity is balanced by the frictional forces, and the resultant force is zero
• Why would a skydiver accelerate towards the ground?

  There is no air resistance acting in the upwards direction, and there is a resultant force acting downwards which accelerates the skydiver towards the ground.
• State Newton’s first law

  An object remains in the same state of motion unless a resultant force acts on it
• If the resultant force is zero, this means..

  A stationary object stays stationary

  A moving object continues to move at the same velocity
• Define uniform motion

  Constant velocity
• State how Newton’s first law works with a car

  When the car travels at a constant speed, the driving force from the engine is balanced by the resistive forces such as air resistance and friction in the cars moving parts. The resultant force on the car is zero
• State how Newton’s first law works with non uniform motion of an accelerating car

  When the car accelerates, the driving force from the engine is greater than the resistive forces. This means that the resultant force is not zero
• State the equation of Newton’s second law

  Resultant force = mass x acceleration (F=ma)
• The equation of Newton’s second law shows that the acceleration of an object is

  Proportional to the resultant force on an object

  Inversely proportional to the mass of an object

  (The acceleration of an object increases if the resultant force increases, decreases if the mass of the object increases)
• State Newton's third law

  When two objects interact, they exert equal and opposite forces on each other
• State the contact forces of pushing a pram (3rd law)

  • The person pushes the pram forwards
  • The pram pushes the person backwards
• State the contact forces of a car tyre on a road (3rd law)

  • The tyre pushes the road backwards
  • The road pushes the tyre forwards
• State the contact forces of a satellite in earth's orbit (3rd law)

  • The earth pulls the satellite
  • The satellite pulls the earth