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Motion and Forces - Coggle Diagram
Motion and Forces
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Momentum
Where p is the momentum in kgms^-1, m is the mass in kg and v is the velocity in ms^-1
In collision, total momentum before = total momentum after
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Momentum is always conserved in a collision (where there are no external forces like
friction, air resistance, electrostatic attraction etc.)
So two marbles colliding, each will have momentum before and after the collision
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For Newtons Second Law, force = change in momentum/time = (mv-mu)/t
Mathematical Skills
Calculate force, mass and gravitational field strength using formulae
Calculate force, mass, velocity and acceleration using formulae
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Estimate the speed, accelerations and forces involved in large accelerations for everyday road transport
Calculate distance, speed and time for...
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Graphs
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Velocity Time Graphs
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Horizontal line, constant speed
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Newton's Third Law
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Rocket taking off
The force of the gases being ejected from the rocket is equal to the force that lifts
the rocket from the surface
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Newton's First Law
If a resultant force acts on the object, it will accelerate
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Vectors & Scalars
What are they?
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Generally, scalar cannot be negative, but vectors can be, as a certain direction is positive
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Scenarios
Imagine a ball is thrown off a cliff, the displacement is 0 at height of cliff, above the cliff the ball has
positive displacement, and below the clifftop the ball has negative displacement
In long answer questions, you may be able to decide where the “0” point of a vector may lie, for example you could set zero to be bottom of cliff, so the ball will never have negative displacement
Speed is only velocity when given a direction, so thrown 10ms^-1 is its speed but thrown 10ms^-1 at 30° above the horizonal is the velocity
Human Reaction Time
Ruler Drop Experiment
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Average this, and 1cm is 50ms, 2cm 60ms, and so on
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There is a delay between a human observing an event, and acting
Circular Motion
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Force
For motion in a circle, there must be a force which supplies this acceleration
This is called centripetal force, and is directed towards the centre of the circle
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Newton's Second Law
Equation
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Where force in in Newtons (N), mass is in kg and acceleration is in ms^-2
Weight
Measured using a force meter, or weighing scales, and is used to work out mass of unknown object
The greater the gravitational field strength, the greater the weight