# Shared Flashcard Set

## Details

OCR Physics A G481
Definitions required for the Mechanics paper
38
Physics
03/17/2011

Term
 Acceleration
Definition
 Rate of change of the velocity of an object
Term
 Velocity
Definition
 Rate of change of the displacement of an object
Term
 Displacement
Definition
 Distance travelled in a particular direction
Term
 Work done
Definition
 The product of the force and the distance moved in the direction of the force
Term
 Linear equilibrium
Definition
 Resultant force is zero (therefore constant velocity - often stationary)
Term
 Rotational equilibrium
Definition
 Resultant torque is zero (therefore constant rate of spinning - usually not spinning)
Term
 Instantaneous speed
Definition
 The speed of an object at a given moment in time
Term
 Average speed
Definition
 The total distance travelled by an object divided by the total time taken
Term
 Scalar
Definition
 Quantity with a magnitude (size) but no direction
Term
 Vector
Definition
 Quantity with a magnitude (size) and a direction
Term
 Elastic deformation
Definition
 The sample returns to its original size and shape when the deforming forces are removed
Term
 Plastic deformation
Definition
 The sample does not return to its original size and shape when the deforming forces are removed
Term
 Ultimate tensile strength
Definition
 The maximum stress that can be applied to an object before it breaks
Term
 Extension
Definition
 The change in length of an object from its original length
Term
 Ductile
Definition
 A material that has a large plastic region (therefore they can be drawn into a wire)
Term
 Brittle
Definition
 A material that distorts very little even when subject to a large stress, and does not exhibit any plastic deformation
Term
 Hooke's Law
Definition
 The extension of an elastic body is proportional to the force producing it
Term
 Elastic limit
Definition
 The point at which elastic deformation becomes plastic deformation
Term
 Elastic potential energy / Strain energy
Definition
 The energy stored in an object (work an object can do) because it is stretched or compressed
Term
 Gravitational potential energy
Definition
 The energy stored in an object (the work an object can do) because of its position in a gravitational field
Term
 Kinetic energy
Definition
 The energy of an object (work an object can do) due to its speed
Term
 Law of Conservation of Energy
Definition
 For a closed system, energy can be transformed from one form into another, or transferred from one place to another, but the total amount of energy remains constant
Term
 The newton
Definition
 1 newton is the force that will give a 1 kg mass an acceleration of 1 m/s^2 in the direction of the force
Term
 Centre of gravity
Definition
 The point where the entire weight of an object can be considered to act
Term
 Moment of a force about a point
Definition
 The force, multiplied by the perpendicular distance from the point
Term
 Torque of a couple
Definition
 The product of one of the forces of a couple and the perpendicular distance between the forces
Term
 A couple
Definition
 Two forces that are equal and opposite but not acting in the same straight line
Term
 The Principle of Moments
Definition
 For an object in rotational equilibrium, the sum of the clockwise moments about any point, equals the sum of the anti-clockwise moments about that same point
Term
 Thinking distance
Definition
 The distance travelled, from seeing the need to stop, to applying the brakes
Term
 Braking distance
Definition
 The distance a vehicle travels while decelerating to a stop
Term
 Stopping distance
Definition
 The sum of the thinking distance and the braking distance
Term
 The joule
Definition
 The work done when a force of 1 N moves its point of application 1 m in the direction of the force
Term
 Power
Definition
 The rate of doing work
Term
 The watt
Definition
 1 joule per second
Term
 Stress
Definition
 The force per unit cross-sectional area
Term
 Strain
Definition
 The extension per unit original length
Term
 Young modulus
Definition
 The ratio of stress to strain, provided Hooke's Law is obeyed
Term
 Equilibrium
Definition
 Resultant force is zero and resultant torque is zero
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