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Moment of a force
turning effect produced when force(s) cause object to turn/ rotate about a pivot
Pivot (fulcrum)
The point about which moments act in a clockwise or anticlockwise direction
The equation linking moment of a force, force and distance
M = Fd
M
The symbol for moment of a force
F
The symbol for force
d
The symbol for distance
Unit for moment of a force
Newton-metre (Nm)
Unit for force
Newtons (N)
Unit for distance
Metres (m)
Principle of moments
the total clockwise moments about a pivot is equal to the total anticlockwise moments in equilibrium
Centre of gravity
The point at which the entire weight of an object can be considered to act
Stable
object resists tipping over as line of action falls within its base
Newton's First Law
An object remains in the same state of motion unless acted on by a resultant force
Resultant force
single force with the same effect as original forces acting together
When the resultant force is zero
object is stationary or continues to move at the same speed/direction
Newton's Second Law
acceleration is proportional to the resultant force acting on the object, and inversely proportional to the mass
The equation linking resultant force, mass and acceleration
F = ma
F
The symbol for force
m
The symbol for mass
a
The symbol for acceleration
Unit for mass
Kilograms (kg)
Unit for acceleration
Metres per second squared (m/s²)
Newton's Third Law
for every action, there is an equal and opposite reaction
Inertia
an object continues in their state of rest or in uniform motion
Inertial mass
how difficult it is to change the velocity of an object or the ratio of force ÷ acceleration
Deformation
change of shape/ size as a result of forces being applied
Conditions required to deform a stationary object
must be more than one force acting on the object
Extension
increase in length/ size as a result of an object being stretched
Compression
reduction in length/ size as a result of an object being squashed
Hooke's Law
extension is directly proportional to force applied, provided limit of proportionality isn’t exceeded
Limit of proportionality
point beyond which Hooke's law is no longer obeyed
The equation linking force, spring constant and extension/compression
F = ke
F
The symbol for force
k
The symbol for spring constant
e
The symbol for extension (or compression)
Unit for spring constant
Newtons per metre (N/m)
Unit for extension
Metres (m)
Spring constant
measure of the stiffness of a spring
Relationship between spring constant and extension
higher the spring constant, the stiffer the spring
Scalar quantity
quantity that has a magnitude (size) only
Examples of scalar quantities
Speed, temperature, mass, energy, distance, density
Vector quantity
quantity that has a magnitude and direction
Examples of vector quantities
Velocity, force, displacement, acceleration, momentum
Representing vector quantities
Vectors are represented by an arrow to indicate its size and direction
Contact forces
Forces between two objects that are physically touching each other
Examples of contact forces
friction, air resistance, tension
Non-contact forces
Forces between two objects that are not physically touching each other
Examples of non-contact forces
gravitational force, electrostatic force, magnetic force
Free body diagram
diagram showing all the forces acting on an object
Friction
contact force that always opposes the motion of an object
Fluid
A liquid or a gas
Pressure
The force per unit area
the equation linking pressure, force and area
p = f/a
p
The symbol for pressure
F
The symbol for force
A
The symbol for area
Unit for pressure
Pascals (Pa)
Unit for area
Square metres (m²)
A unit used for pressure that is equivalent to pascals (Pa)
Newtons per metre squared (N/m²)
How to increase pressure
Increase the force or decrease the area
How to decrease pressure
Decrease the force or increase the area
Mass
the amount of matter in an object
Weight
force acting on an object due to gravity
Relationship between weight and mass
directly proportional to one another
The equation linking weight, mass and gravitational field strength
W = mg
W
The symbol for weight
m
The symbol for mass
g
The symbol for gravitational field strength (gravity)
Unit for gravitational field strength
Newtons per kilograms (N/kg)
Centre of mass
point the weight of an object may be considered to act at
Newton meter
calibrated spring-balance used to measure an object's weight
Note 
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