# forces and motion

• forces and motion
• speed= distance/time
• m/s
• acceleration=(final velocity-initial velocity)/time
• a=(v-u)/t
• m/s/s
• scalar- magnitude (size)
• distance
• mass
• speed
• vector- magnitude and direction
• displacement
• weight
• velocity
• acceleration
• force
• momentum
• v2-u2=2x a x d
• velocity/time graph
• gradient = acceleration
• ---- steady speed
• the steeper the graph, the greater the acceleration
• / acceleration
• \ deceleration
• area under the graph = the distance
• distance/time graph
• gradient = speed
• ----- where it stopped
• steeper the faster
• \ goes backwards
• curving means its speeding up
• weight = mass x gravitational field strength
• weight is caused by the pull of gravity. mass is the same value anywhere
• mass- Kg
• weight- (N) Newtons
• forces
• gravity/weight
• reaction force
• thrust
• lift
• tension
• drag/ air resistance/ friction
• electrostatic force
• Terminal Velocity
• the resistance force is equal to the accelerating force
• the accelerating force acting on a falling object is gravity
• newtons laws
• 1st law
• balanced forces mean no change in velocity
• as long as the forces on an object are all balanced, then the object will stay still, or continue moving at a constant velocity
• 2nd law
• if there is an unbalanced force, then the object will accelerate in that direction
• force= mass x acceleration
• resultant force- the single force that replaces all forces acting on an object found by adding these together, if the forces are balanced the resultant force is zero
• 3rd law
• if object A exerts a force on object B then object B exerts the exact opposite force on object A.
• momentum
• momentum = mass x velocity
• p=m x v
• Kg m/s
• conservation of momentum
• in a closed system
• total momentum before an event = total momentum after the event
• When a cannon is fired, the cannon ball gains forward momentum and the cannon gains backward momentum. Before the cannon is fired, the total momentum is zero. This is because neither object is moving. The total momentum of the cannon and the cannon ball after being fired is also zero, with the cannon and cannon ball moving in opposite directions.
• force= (mv-mu)/t
• car safety all reduce the rate of change of momentum
• seat belt
• air bag
• rear crumple zone
• front crumple zone
• motion of vehicles
• stopping distance= thinking distance + breaking distance
• thinking distance is affected by...
• drugs
• alcohol
• caffeine
• tiredness
• distractions
• breaking distance is affected by...
• road surface
• weather
• tyre condition
• mass of the vehicle
• speed
• when a force is applied to the brakes of the vehicle, work is done, friction is created reducing the kinetic energy
• work done= force x distance
• KE= 1/2 x mass x velocity2

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