# P4 - Explaining motion

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• Created by: dmistry02
• Created on: 11-06-14 11:32
• P4 - Explaining motion
• movement
• speed
• distance travelled in a certain time
• The speed often changes
• we calculate average speed.
• Distance (m) / Time Taken (s)
• we calculate average speed.
• how fast something is
• Velocity
• speed and direction
• can be positive and negative
• Distant time Graph
• Gradient = speed
• Flat section = Stationary
• Down hill = returning
• steepening curve = accelarating
• levelling off curve = decelarating
• Velocity-Time graph
• Gradient = acceleration
• flat section = constant speed
• curve  = changing acceleration
• Acceleration
• Change in velocity (m/s) /time take (m)
• unbalanced force
• thrust is stronger than drag
• Forces
• occur when to objects interact
• Friction
• 3 types of friction
• Friction between solid surfaces which are gripping (allows you to walk)
• Friction between solid surfaces sliding past each other
• Resistance or drag from fluids (air resistance)
• moving objects experience friction.
• arrows shows the size and direction of a force.
• steady speed has a balanced force
• reaction of a surface has a balanced force
• resultant force
• overall force acting on the object
• determines the movement
• causes acceleration
• Momentum (kg m/s)
• Acceleration
• Change in velocity (m/s) /time take (m)
• unbalanced force
• thrust is stronger than drag
• Mass (kg)  x Velocity (m/s)
• Change in Momentum (kg m/s)
• resultant force acts on an object
• Resultant force (N) x Time for which the force acts (s)
• Car safety
• crumple zones
• increase stopping time
• less impact on driver
• Less shock on the nerves
• Airbags
• increases stopping time
• Seat belts
• increases stopping time
• reduces force on the chest
• helmets
• padding absorbs some of the force
• increases the time for the head to come to a stop
• Work
• Kinetic Energy
• energy of movement
• 1/2 x mass (kg) x Velocity2 (m/s2)
• increase in kinetic energy = work done
• energy is lost in the surrounding
• heat
• sound
• work done (J) = Force (N) x Distance moved in direction of the force (m)
• requires a supply of enery
• food
• fuel
• electricity
• when a force moves an object it does work and energy is transferred to the object
• Gravitational potential energy
• increasing height = increasing G.P.E
• Change in G.P.E = weight (N) x Vertical height difference
• Falling objects convert G.P.E into K.E
• Kinetic Energy
• energy of movement
• 1/2 x mass (kg) x Velocity2 (m/s2)
• increase in kinetic energy = work done
• energy is lost in the surrounding
• heat
• sound
• K.E gained = G.P.E lost
• Amount of energy transferred (J) = Work Done (J)
• Work
• work done (J) = Force (N) x Distance moved in direction of the force (m)
• requires a supply of enery
• food
• fuel
• electricity
• when a force moves an object it does work and energy is transferred to the object
• Gravitational potential energy
• increasing height = increasing G.P.E
• Change in G.P.E = weight (N) x Vertical height difference
• Falling objects convert G.P.E into K.E
• K.E gained = G.P.E lost