forces and motion

• what is a vector

  quantities that have both a magnitude and direction
• scalar


  quantity with only a magnitude
• examples of scalar quantities

  • distance
  • energy
  • temperature
  • mass
  • speed
• examples of vector quantities

  • force
  • weight
  • displacement
  • acceleration
  • velocity
• displacement


  a measurement from where you start from and end
• what is the displacement if you go from you house to your school and then return home?


  0
• average speed =

  total distance/total time
• what is the gradient in a distance-time graph

  velocity
• what does a horizontal line mean in a distance-time graph?


  it is stationary
• how to calculate gradient


  rise/run
• acceleration


  The change in velocity per unit time
• acceleration =


  change in velocity / time taken
• unit of acceleration


  m/s^2
• gradient in a velocity-time graph


  acceleration
• what does it mean if speed is zero on a velocity-time graph


  its at rest
• horizontal line on a velocity-time graoh

  constant speed
• area under the line on a velocity-time graoh


  the distance travelled
• what is the value of acceleration due to gravity?


  10 m/s^2 on earth
• velocity =


  speed/time
• final velocity =


  initial velocity + acceleration * time
• final velocity ^2 =


  initial velocity ^2 + 2 * acceleration * distance
• how could we measure the value of the acceleration of a handbag when it is dropped


  -drop it from a certain height

  -use a light gate to measure the velocity of the handbag

  -time it so you can calculate acceleration by

  dividing the final velocity by the time
• contact forces

  • friction
  • air resistance
  • water resistance
• non-contact forces

  • elastic force
  • electrostatic force
  • magnetic force
  • weight
  • gravity
• friction


  a force between two surfaces which opposes motion and results in heating due to the transfer of energy
• how to find resultant force of two or more forces acting along the same line

  the should be added together if in the same direction and subtracted if in the opposite direction
• resultant force


  a single force that describes all of the forces acting on a body
• newtons 1st law


  a body will remain stationary or move at a constant velocity unless acted upon by a resultant force
• newtons 2nd law


  the acceleration is proportional to the applied resultant force and acts in the same direction as the force
• force =


  mass * acceleration
• if the mass of an object is doubled and the resultant force on it stays the same, what will happen to the acceleration which the object experiences?

  It will stay the same because the resultant force is directly proportional to the acceleration
• weight =

  mass * gravitational field strength
• mass

  is a measure of how much matter is in an object

  measured in Kg
• weight


  weight a gravitational force

  measured in newtons(N)
• gravitational field strength on earth


  10 N/Kg
• what does the weight of an object act through


  its center of gravity
• free fall


  objects that fall only due to the influence of a gravitational field
• all objects fall with the same acceleration if there is no

  air resistance
• Terminal velocity of a skydiver


  -As the skydiver jumps there isn't much air resistance acting on them but the initial force of weight causes them to accelerate downwards.

  -As they accelerate, the air resistance increases until both forces of air resistance and weight balance out and there is no resultant force or acceleration so the skydiver reaches terminal velocity
• terminal velocity of skydiver after opening parachute

  -After opening the parachute, the air resistance increases so they begin to decelerate as the resultant force is smaller.

  -As they slow down, the air resistance decreases until the air resistance and weight balance which means they have terminal velocity as there is no resultant force or acceleration