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Forces and motion / Mechanics (OCR Physics A)
Key words and definitions for Unit G481 (Mechanics) of OCR Physics A (AS Level). Created by Rob Cowen, Head of Physics (www.cowenphysics.com).
The force which gives a mass of 1kg an acceleration of 1ms^-2.
The work done by a force of 1 N moving an object 1 m in the direction of the force.
The power transferred by one joule per second.
the distance moved by an object in a particular direction
the speed at the precise instant that it is measured (e.g. a car's speedometer)
the speed calculated during a period of time
rate of change of distance
rate of change of displacement
rate of change of velocity
mass / volume
torque of a couple
one of the forces x perpendicular distance between the forces.
moment of a force
force x perpendicular distance from pivot.
work done by a force
force x distance moved in the direction of the force
the rate of work done
force constant of a spring
force per unit extension
a quantity with magnitude only
a quantity with both magnitude and direction
the velocity of a falling object when weight = drag
centre of gravity
a point where the entire weight of an object appears to act
the distance travelled by the car in the time taken by the driver to react
the distance travelled by the car after the brakes are applied until the car stops
thinking distance + braking distance
principle of conservation of energy
Energy cannot be created or destroyed; it can only be transferred into other forms
principle of moments
For an object in equilibrium, the sum of the clockwise moments about a point = the sum of the anticlockwise moments about the same point
extension of a spring is proportional to the force applied (as long as the elastic limit is not exceeded)
= force / area
= extension / original length
= stress / strain, as long as the elastic limit is not exceeded
ultimate tensile strength
the breaking stress of a material
material returns to original shape when the force is removed
material does not return to original shape when the force is removed
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