GCSE Physics Edexcel P2 Topic 3

These are revision notes I made myself. I got A* in the Physics GCSE exam and 80 UMS (full marks) in the P2 exam using only these notes.

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P2 Topic 3: Motions and Forces
Displacement: a straight line from start to finish. It is a quantity with a certain direction as it must go in a
straight line.
Speed: This tells you how quickly an object will travel a certain distance. It can worked out by the following
distance (m)
equation: speed (m/s)= time taken (s)
Velocity: Tells how quickly an object is moving but also which direction the object is moving.
Quantities like displacement and velocity are called vector quantities as they both have a size and a direction.
Force is also a vector quantity. For example, on the Earth the weight of an object is always pulled vertically
downwards.
Distance-time graphs
A graph in which distance is plotted against time is called a distance-time graph. As time and distance are
both used to calculate speed, the graph can tell you a lot of things about speed:
o horizontal lines = stationary object
o straight, sloping lines mean the object is travelling at constant speed
o steeper the line = faster the object is travelling
o Curves represent acceleration and deceleration. Levelling off means slowly down.
o Downhill means going back to its starting point.
o speed can be calculated from the gradient of the line
o distance from the graph
time from the graph
Acceleration
Acceleration: A change in velocity in a moving object. It is a vector quantity as it has a magnitude and a
direction.
Acceleration can be calculated using the following equation: acceleration (m/s2) = change in velocity (m s)
time taken (s)
(v-u)
Or written in symbols: a = t wherein
o a is the acceleration
o v is the final velocity
o u is the initial velocity
o t is the time taken for the change in velocity

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The acceleration tells you the change in velocity each second so the units of acceleration are metres per
second, per second. This is written as m/s2. An acceleration of 10m/s2 means that each second the velocity
increases by 10 m/s.
Acceleration is for both getting faster and getting slower.
During a part of a landing sequence for the Space shuttle, it slowed down from 70 m/s to 20 m/s in 20
seconds. Therefore:
s-70 m s = ( -50 m s ) = -2.…read more

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Forces
Forces can make objects change speed, shape or direction. A force is also a vector quantity because it has
both size and direction. Most objects have more than one force acting on them.
A free-body diagram shows the difference forces acting upon one object, with their size and direction.
Action and reaction forces
Whenever two objects touch they interact with each other. This interaction involves two forces, acting on
difference objects.…read more

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If the same force is applied to two objects, the one with the smaller mass will accelerate more. If two objects
of difference mass are to have the same acceleration, then a large force must be applied to the object with
the greater mass.…read more

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When an object begins to fall from above the Earth, the only force acting on it is its weight. As it gains speed
air resistance begins to act in the opposite direction, reducing the resultant force.
The resultant force on the falling skydiver changes. As with all objects, eventually the weight and air
resistance forces are balanced. The resultant force on the skydiver is then zero, so they will stop
accelerating. They will travel at a constant velocity, called the terminal velocity.…read more

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