Forces & Motion
Speed & Velocity
• Average speed = total distance travelled ÷ time taken
• speed & distance are scalar quantities (magnitude only)
• velocity - the speed in a given direction
• displacement - the distance in a given direction
• both vector quantities (have magnitude and direction)
Distance-Time Graph
• horizontal line - no gradient, stationary (speed = 0)
• uphill line - constant gradient, constant speed (in the positive direction)
• downhill line - constant gradient, constant speed (in the negative direction)
• curved line - gradient increasing, accelerating (speed increasing)
• curved line - gradient decreasing, decelerating (speed decreasing)
• gradient of the graph = speed
Acceleration
• instantaneous speed - the speed of an object at a speci c moment in time
• acceleration - the rate at which velocity is changing
• speeding up/slowing down/changing direction
• acceleration = ( nal velocity - initial velocity) ÷ time taken
• another equation linking acceleration & distance: v^2 = u^2 + 2as
Velocity-Time Graph
• represents how an object’s velocity can change over time
• horizontal line - no gradient, constant velocity
• uphill line - constant gradient, constant acceleration
• downhill line - constant gradient, constant deceleration
• curved line - gradually changing acceleration
• gradient of the graph = acceleration (can be positive or negative)
• area under the graph = distance travelled
Forces
• causes acceleration (speeds up/slows down/changes direction) of an object
• can also change the shape or size of an object
• contact forces - require physical touch
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, • non-contact - act at a distance through elds, affecting objects without touching
Contact Non-Contact
Friction Gravitational
Push/Pull Magnetism
Air Resistance Electrostatic
Upthrust Strong Nuclear
Tension
Newton’s Laws
Newton’s 1st Law
• a body will remain at rest or move at a constant velocity unless acted upon by an
unbalanced force
Newton’s 2nd Law
• acceleration is directly proportional to the resultant force and is inversely
proportional to its mass
• F = ma
Newton’s 3rd Law
• if body A exerts a force on body B, then body B will exert an equal force on body A
but in the opposite direction
Momentum
• the product of mass and velocity
• vector - has both magnitude and an associated direction
• stationary objects have no momentum - the velocity is zero
• the faster an object moves (greater the velocity), the bigger the momentum will be
• the heavier an object is (bigger the mass), the bigger the momentum will be
• p = mv
The Law of Conservation of Momentum
• when 2 or more objects collide:
• total momentum before collision = total momentum after collision
Vehicle Safety & Momentum
• the force applied to an object = the rate of change of momentum
• f = ∆p/t
fi
Speed & Velocity
• Average speed = total distance travelled ÷ time taken
• speed & distance are scalar quantities (magnitude only)
• velocity - the speed in a given direction
• displacement - the distance in a given direction
• both vector quantities (have magnitude and direction)
Distance-Time Graph
• horizontal line - no gradient, stationary (speed = 0)
• uphill line - constant gradient, constant speed (in the positive direction)
• downhill line - constant gradient, constant speed (in the negative direction)
• curved line - gradient increasing, accelerating (speed increasing)
• curved line - gradient decreasing, decelerating (speed decreasing)
• gradient of the graph = speed
Acceleration
• instantaneous speed - the speed of an object at a speci c moment in time
• acceleration - the rate at which velocity is changing
• speeding up/slowing down/changing direction
• acceleration = ( nal velocity - initial velocity) ÷ time taken
• another equation linking acceleration & distance: v^2 = u^2 + 2as
Velocity-Time Graph
• represents how an object’s velocity can change over time
• horizontal line - no gradient, constant velocity
• uphill line - constant gradient, constant acceleration
• downhill line - constant gradient, constant deceleration
• curved line - gradually changing acceleration
• gradient of the graph = acceleration (can be positive or negative)
• area under the graph = distance travelled
Forces
• causes acceleration (speeds up/slows down/changes direction) of an object
• can also change the shape or size of an object
• contact forces - require physical touch
fi fi
, • non-contact - act at a distance through elds, affecting objects without touching
Contact Non-Contact
Friction Gravitational
Push/Pull Magnetism
Air Resistance Electrostatic
Upthrust Strong Nuclear
Tension
Newton’s Laws
Newton’s 1st Law
• a body will remain at rest or move at a constant velocity unless acted upon by an
unbalanced force
Newton’s 2nd Law
• acceleration is directly proportional to the resultant force and is inversely
proportional to its mass
• F = ma
Newton’s 3rd Law
• if body A exerts a force on body B, then body B will exert an equal force on body A
but in the opposite direction
Momentum
• the product of mass and velocity
• vector - has both magnitude and an associated direction
• stationary objects have no momentum - the velocity is zero
• the faster an object moves (greater the velocity), the bigger the momentum will be
• the heavier an object is (bigger the mass), the bigger the momentum will be
• p = mv
The Law of Conservation of Momentum
• when 2 or more objects collide:
• total momentum before collision = total momentum after collision
Vehicle Safety & Momentum
• the force applied to an object = the rate of change of momentum
• f = ∆p/t
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