Scalar
quantities with only magnitude such as speed, distance, time and mass.
Vector
quantities with a magnitude and direction e.g. acceleration, force momentum and weight. A vector quantity can be represented as an arrow, the size representing the magnitude and the direction, the direction.
No...
Scalar
quantities with only magnitude such as speed, distance, time and mass.
Vector
quantities with a magnitude and direction e.g. acceleration, force
momentum and weight. A vector quantity can be represented as an arrow,
the size representing the magnitude and the direction, the direction.
Non-contact force
the objects are physically separate e.g.
magnetism/gravity/electrostatic.
3 non-contact forces
magnetism
gravity
electrostatic
Contact force
objects are physically touching .
3 contact forces
friction
resistance
tension
Gravity
Weight is the force acting on an object due to gravity, it acts on an
objects 'centre of mass' and is directly proportional to mass
Weigh Equation
Weight = mass x grav. field strength
Resultant forces
A number of forces acting on an object may be replaced by a single
force that has the same effect as all the original forces acting
together, this single force is the called the resultant force.
In a tug of war, 1000N to the left and 800N to the right. The
resultant force is 200N to the left
Free-Body force diagrams
,When an object is acted on by more than one force you can draw a
free-body force diagram to work out the resultant force on the object.
It shows the forces acting on an object without any other objects or
other forces shown. Each force is shown on the diagram by a vector,
which is an arrow pointing in the direction of the force. ( the
normal force is that component of the contact force that is
perpendicular to the surface that an object contacts)
How to resolve forces (force diagram steps)
1. Decide on a scale of N per cm.
2. Draw the 2 given forces, giving respect to their length (more cm
if more N) and the angle that you are given
3. Draw a line connecting the end of the 2 other lines to form a
triangle
4. Measure the length of this line, then convert it to N by using the
scale
Relationship between Joules and work done
When a force causes and object to move, work is done on the object so
when the force causes displacement. One joule of work is done when a
force of 1 newton displaces an object 1 metre. 1 Joule = 1 newton-
metre.
Equation for word done
work done = force x distance
Elastic Deformation
When an elastic object is stretched, bent, twisted or compressed it
will return to its original form
Inelastic Deformation
Polyethene bags will not return to their original shape after being
deformed, this is inelastic.
Hooke's Law
The extension of an elastic object is directly proportional to the
force applied as long as the limit of proportionality is not exceeded:
Equation for force (Hooke's law)
force = spring constant x extention
Extension and compression's relationship with elastic potential
energy explanation
A force that stretches or compresses a spring does work and elastic
potential energy is stored in the spring, provided the spring is not
elastically deformed, the work done and elastic potential energy are
equal. Before the limit of proportionality is breeched the
relationship is linear (directly proportional) afterwards it is non-
linear
, Elastic potential energy equation (given)
Elastic potential energy = 1/2 x spring constant x extension^2
Moment meaning
The turning effect of a force is called its 'moment'
Moment equation
moment = force x distance
Balancing
If an object is balanced the clockwise moment is equal to the
anticlockwise moment.
Levers
A lever consists of a load, effort and pivot, levers use moments to
multiply a force, they allow a larger force to act on the load that
is supplied by the effort.
Engine Gears
Engine gears have two main jobs, producing torque and speed, however
they are inversely proportional so gears are made to make a
compromise between the two in any given situation.
When starting a car we want high torque, which means being able to
carry a greater load , and consequentially less speed. In low gears
this is achieved as...
1. The engine causes a small cog on the engine axle to rotate.
2. The small cog on the engine axle is connected to a larger cog on
the wheel axle, which increases the torque (moment) exerted.
3.A high turning force but low speed is exerted on the wheel (low
gear)
When a car is already moving, we want a high speed which is achieved
as...
1.The engine causes a larger cog on the engine axle to turn.
2.The larger cog on the engine axle is connected to a smaller cog on
the wheel axle, causing a high rate of rotation, but a low turning
force.
3. The wheel rotates quickly, causing a high speed
Unit for pressure
Pressure is a measure of force per unit of area, the si unit is
Pascals (Pa) which is one N/m^2
Pressure Equation
Pressure = force normal to the surface/area
Manometer with oil and water
The pressure is equal at each end of the tube, so the less dense oil
is higher.(p=hdg)(on sheet)
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