p8 - forces in balance Flashcards
define quantity
anything that can be given a numerical value
define magnitude
- size of quantity
- e.g: distance of 5m has a higher magnitude than distance of 2m
define scalar
- describes quanitites that only have a magnitude
- e.g: speed
define vector
- descibes quantities with magnitude AND a specific direction
define a force
- a vector quantity
- pushes or pulls acting on an object
- has size and direction
- result of objects interacting with eachother
define contact forces
for these to act, the interacting objects have to be physically touching
define non-contact forces
for these to act, interacting objects don’t have to be physically touching
define resultant force
single overall force acting on an object
list scalar quantities
distance
speed
mass
temperature
pressure
volume
work
list vector quantities
displacement
velocity
acceleration
force
weight
momentum
give 4 examples of contact forces
1) friction
2) air resistance
3) tension
4) the normal contact force
give 3 examples of non-contact forces
1) gravitational force
2) electrostatic force
3) magnetic force
why are free-body diagrams useful?
they help us show all forces acting on an object
why is it useful to show magnitude and direction in a diagram?
- forces are vector values
- arrow points in direction
- length refers to magnitude
how are forces represented?
using vector diagrams
how do you represent resultant force on a diagram?
- combine the arrows by appropriately adding or subracting them
in which circumstances would the resultant force be zero?
- when forces acting on an object are equal in magnitude and opposite in direction
- forces are balanced
what impact does a resultant force of zero have on an object?
has no impact, movement will not change
when would you use vector diagrams?
to break down a single force into two forces acting at right angles to each other
what is the parallelogram rule used for?
used to find resultant force when forces don’t act in the same line
describe the parallelogram rule
watch freesciencelessons video to check knowledge on this
define ‘work done’
- the measure of how much energy is transferred when a force makes an object
- always involves transfer of energy
- scalar quantity
define a joule
- the unit joule (J) is how energy transfer by work done is measured
- 1 joule = 1 newton metre
- this means that 1 J is
the amount of work done when a force of 1 N causes an object to move 1 m
define distance
- how far an object moves
- scalar quantity (no direction)
define displacement
distance in a certain direction
define friction
contact force resulting when two object move past and touch eachother
how can amount of work be calculated?
W = Fs
work done (J) = force (N) x distance (m)
what happens when work is done against friction?
- an energy transfer to heat is caused
- raises temperature of the object and surroundings
what is newton’s first law?
if resultant force of an object is zero,
- stationary objects stay stationary
- moving objects keep moving at same velocity
define stationary
not moving, resultant force of zero
define inertia
the tendency of objects to stay at the same speed or stay stationary
what is newton’s second law?
- objects accelerate if there is a resultant force acting on them
- amount of acceleration is proportional to magnitude of resultant force and inversely proportional to the mass of an object
what is newton’s third law?
when objects interact, the force they cause to react to each other are equal and opposite
define intertial mass
a measurement of an object’s resistance to changes in motion until enough external force is applied
give the resultant force equation
F = m a
resultant force (N) = mass (kg) x acceleration (m/s squared)
