Zusammenfassung der Ressource
Forces 1
- Quantities
- Scalar
- Scalar quantities only have magnitude (size)
- Vector
- Vector quantities have both
magnitude and direction
- These can be represented
by arrows
- Length of arrow
determines
magnitude
- Direction of arrow
represents
direction
- Contact and
Non-contact
forces
- A force is a push or pull that
acts on an object due to the
interaction with another object
- contact forces – the objects are
physically touching
- Friction
- Air
resistance
- non-contact forces – the objects
are physically separated
- Gravitational
force
- Magnetic Force
- Weight and Gravity
- Weight = mass x Gravity
- W = mg
- Weight, W, in Newtons, N
- mass, m, in kilograms, kg
- gravitational field strength, g, in N/kg
- The weight of an object is directly
proportional to mass
- Mass is how much matter
is contained within a
body.
- Mass remains
constant regardless
of gravity
- Weight is the force of
gravity acting upon a
mass
- The weight changes
according to the
gravitational field strength
- Weight is measured using
a Newtonmeter
- Work done and
Energy Transfer
- A resultant force is the
overall representation of all
of the forces acting upon a
body
- It is a single force that has
the same effect of
multiple forces combined
- Work done = Force x distance
- W = F x s
- Work done, W, in joules, J
- distance, s, in metres
- Force, F, in newtons, N
- One joule of work is done when a
force of one newton causes a
displacement of one metre
- 1 joule = 1 newton-metre
- Forces and Elasticity
- Deformation
- This means to change an object's shape
- force = spring constant x extension
- F = k x e
- Force, F, in newtons, N
- spring constant, k, in
newtons per metre, N/m
- extension, e, in metres, m
- This relationship also applies to the
compression of an elastic object, where ‘e’
would be the compression of the object
- When a force stretches or
compresses a spring work
is done
- Elastic potential
energy is then
stored
- Provided the spring is
not deformed...
- The work done on the
spring and stored elastic
potential energy will be
equal
- Moments
- Moment = Force × distance
- M = F x d
- moment of a force, M, in
newton-metres, Nm
- force, F, in newtons,
N
- distance, d, in metres, m
- This is is the perpendicular
distance from the pivot to the
line of action of the force
- If an object is balanced, the total clockwise
moment about a pivot equals the total
anticlockwise moment about that pivot