# Mechanics Keywords

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• Created by: Vikzy
• Created on: 09-02-13 18:21
Speed
Rate of change of position. Speed =∆s/∆t
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Average Speed
Value of speed obtained by dividing the total distance covered by the time taken. This may be very different from the instantaneous speed.
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Instantaneous speed
The speed at which an object s travelling at a particular time.
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The slope of a graph (gradient = change in y-value ÷ change in x-value). The gradient is the value of m in the equation y=mx+c
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Linear
Two quantities that are related by a linear relationship are proportional to each other. If the quantity of one value doubles, so does the other.
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Intercept
The point of the axis on a graph where a line drown through the plotted points meet the axis.
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Displacement
Distance moved from a reference point. Displacement is a vector quantity
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Scalar
A quantity that has magnitude or size, but no direction. Mass is a scalar quantity.
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Magnitude
Size. A scalar quantity has magnitude, but a vector quantity has both magnitude and direction
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Vector
A quantity that ha both magnitude and direction. Velocity if a vector quantity.
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Accelerates
To increase velocity.
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Acceleration
The rate of change in velocity with time. Given by (final velocity – initial velocity)÷ time taken for change.
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Base Units
The seven fundamental units on which the SI system if units is based. These include units for mass (kg), length (m), time (s), electric current (A) and thermodynamic temperature (K).
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Derived Units
SI units can be combined to give derviced units. Such as speed (ms-1)
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Resultant
The result of combining two or more vectors, for example vectors.
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Relative motion
The motion of one object in relation to another.
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Newton’s First Law
Every object continues in its state of rest or uniform motion in a straight line unless made to change by the total force acting on it
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Free Body Diagram
A diagram to show all the forces acting on a body in a certain situation
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Centre of gravity
A point through which all the weight of an object appears to act.
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Centre of mass
A point through which all the mass of an object appears to be concentrated.
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Friction
Resistance to movement caused by small-scale roughness of the surfaces in contact.
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Aerodynamic drag
The friction force experienced by an object a it moves through air
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Acceleration of free fall
The acceleration due to gravity. On earth the acceleration due to gravity is 9.81ms-1
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Newton’s second law of motion
The acceleration of an object is directly proportional to the magnitude of the net force of an object in the same direction as the net force, and inversely proportional to the mass of an object. F=ma
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Mass
The amount of matter in an object. The unit is (kg)
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Gravitation
The attractive force between tow bodies due to their mass.
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Gravitational field
The field around a mass which causes it to attract another mass which is close to it.
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Gravitational field strength
The force per unit mass acting at that object.
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Weight
The force of gravity on an object. W = mg
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Newtons third law of motion
If body A exerts a force on body B, then body B exerts a force of the same size on body A, but in the opposite direction.
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Equilibrium
A steady state. The forces on a body in equilibrium are balanced.
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Statics
The study of forces on objects that are not moving.
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Parallelogram rule
The resultant of two vectors can be found by drawing a parallelogram with the two vectors to be added as the sides. The diagonal of the parallelogram is the resultant
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Resultant force
The total force of an object that result from the combination of the forces acting on it.
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Projectile
An object given an initial velocity that then moves under a constant force, for example the force of gravity.
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Law of conservation of energy
Energy cannot be created or destroyed
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Theories
An explanation or model of the way matter behaves that can be tested through experiment.
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Hypothesis
A proposal put forward to explain facts or explanations that can be tested by further investigation.
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Peer-review
Process by which research is scrutinised for accuracy and quality by others working in the field before it’s published.
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Chemical Potential Energy
The energy in chemical bonds holding the atoms of a compound together, which can be released by a chemical reaction
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Gravitational potential energy
Potential energy stored in an object due to its position
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Energy Transfer
The process by which energy is transferred from one object to another. For example by heating or working.
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Work
Work done = force x distance moved in direction of force
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Kinetic energy
Energy due to motion. K = 1/2mv2
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Efficiency
The ratio of energy output to energy input. Efficiency is usually given as a percentage: efficiency =useful energy output/ total energy input x 100%
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Horsepower
The unit of power used to describe the power of a car’s engine. 1HP = 750W
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## Other cards in this set

### Card 2

#### Front

Value of speed obtained by dividing the total distance covered by the time taken. This may be very different from the instantaneous speed.

Average Speed

### Card 3

#### Front

The speed at which an object s travelling at a particular time.

### Card 4

#### Front

The slope of a graph (gradient = change in y-value ÷ change in x-value). The gradient is the value of m in the equation y=mx+c

### Card 5

#### Front

Two quantities that are related by a linear relationship are proportional to each other. If the quantity of one value doubles, so does the other.