# Forces

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• Created by: Clare
• Created on: 24-10-12 18:59
• Forces and Motion
• Velocity
• Terminal Velocity
• Mass and air resistance are balanced
• Zero resultant force
• Sky diver
• As they fall they speed up.
• More air resistance= less acceleration
• Force from drag balances due to gravity(terminal velocity)
• Parachute opens, increased air resistance
• Eventually rebalances at a much lower terminal velocity
• Opposing forces are balanced so there is a constant velocity
• Affected by: Weight, Surface area, Amount of force
• Speed in a given direction
• m/s
• Resultant Force
• SUM of all forces acting on a body
• Objects going the same way
• ADD to find resultant force
• Objects pulling away from each other
• SUBTRACT
• Stationary
• Zero forces
• Constant Velocity
• Balanced forces
• Acceleration
• Unbalanced forces towards direction of motion
• Decceleration
• Unbalanced forces against direction of motion
• Mass x Acceleration
• Acceleration
• Acceleration= change in velocity / time
• Change in velocity= final- initial value
• Deceleration= negative
• Speed
• Stopping distance
• Thinking + Braking
• Thinking- reaction time
• Affected by: Drugs, Tiredness, Age, Distractions, SPEED
• Braking- distance between hitting brakes and stopping
• Affected by: Road surface, quality of brakes and tyres, SPEED
• Distance taken for moving object to stop
• Distance/ Time graph
• Horizontal= stopped
• Straight line= constant speed
• Steeper= faster
• Speed= Distance/ Time
• Momentum
• Momentum BEFORE= Momentum AFTER
• Conservation of momentum
• IF no other forces are acting
• Momentum= Mass x Velocity
• Velocity= m/s
• Mass= kg
• Momentum= kg m/s
• Add total momentum before collision
• Rearrange knowing momentum after to find missing vaue
• Moments
• Moments make things turn or rotate around a point
• Moments= Distance from pivot x Mass
• Lift more weight= more distance between pivot and force
• Have direction- clockwise or anticlockwise
• Measured in Nm (Newton Metres)
• Fixed point- pivot or fulcrum
• Mass, Weight, Gravity
• Mass: amount of matter in the object
• Different per object but doesn't change from earth to moon
• Weight: force of gravity acting
• On earth stays the SAME
• Gravity: field created by any object with mass
• 10N per kg Towards the centre of the earth
• ALL objects fall at the same speed due to gravity always acting
• On earth: objects with a larger surface area fall slower due to air resistance
• Mass= weight            gravity