Force and Motion

• Newton's first law:

  An object remains at rest or continues to move at a constant velocity, unless acted on by another force.
• Newton's 2nd law

  Force = mass x acceleration
• Newton's 3rd law

  Every action has an equal opposite reaction
• Inertia is the tendency of an object to remain in uniform motion or at rest
• inertia mass = force needed to change velocity/acceleration from change in velocity
• Acceleration occurs when the resultant force is in the same direction as the velocity
• weight of an object is the force exerted on an object
• weight (n) = mass (kg) x gravitational field strength (n/kg)
• Mass is the quantity of matter
• terminal velocity: where the forces (usually weight and drag) are balanced and the resultant force is 0N. This means that the speed remains constant
• force = mass x initial velocity/time taken
• acceleration = final velocity - initial velocity/ time taken
• thinking distance: distance travelled during the time it takes for the driver to reacr
• braking distance: distance travelled until stationary after brake pedal pressed
• stopping distance = thinking distance + braking distance
• momentum = mass x velocity
• momentum: the quantity of motion that is made up of matter moved + velocity it moved at
• conservation of momentum: when two objects collide, the total momentum of those objects before the collision is equal to it after.
• elastic collision properties:

  • velocity reduced
  • momentum conserved
  • kinetic energy conserved
• non - elastic collision properties:

  • kinetic energy converted to thermal energy
  • momentum conserved - objects collide from opposite directions resultant force = momentum. both would be 0n.
• extension = extended length - original length
• Hooke's law - extension of the spring is directly proportional to the force applied to the spring, provided its limit of proprotionality is not exceeded
• force = spring constant (k, N/M) x extension
• spring constant = gradient
• the steeper the gradient, the higher the spring constant
• factors affecting stopped distances:

  tiredness

  drugs or alcohol

  poorly maintained vehicle

  wet or icy roads

  distractions