Forces - Newtons 2nd law of motion

• 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
• Calculating force required to accelerate an object

  Force (N) = Mass (kg) x Acceleration (m/s^2)
• Estimating speed, acceleration and forces for everyday road transport

  • Cars travel around 13 m/s on main roads, 30 m/s on motorways
  • Typical acceleration from main road to motorway is around 2 m/s^2
  • Typical force required for a family car is around 2,000 N
• Inertia


  An object will stay stationary or continue moving at the same speed and direction unless a resultant force is applied
• Inertial mass


  A measure of how difficult it is to change the velocity of an object, defined as the ratio of the force needed to accelerate an object over the acceleration produced
• An object with a large inertial mass will require a larger force to produce a given acceleration
• An object with a smaller inertial mass will require a smaller force to produce a given acceleration