P5 Forces and Density Flashcards
how do you calculate mass?
volume x density
or
weight / gravity
how do you measure the volume of an irregular object?
displacement of water
how do you calculate density?
mass/volume
how do you calculate volume?
mass/density
what is the tool used to measure very small distances?
micrometer screw gauge
what is force?
a PUSH/PULL that can change the SIZE, SHAPE and MOTION of a body
what is force measured in?
Newtons (N)
how do we draw force diagrams?
ARROW shows direction
LABEL (…N) shows magnitude
what is a resultant force?
the net force acting on an object
what happens when forces are balanced?
- no resultant force
- object at rest or constant speed in straight line
what happens when forces are unbalanced?
- there’s a resultant force
- the object accelerating or decelerating
F = ?
ma (newton’s 2nd law)
kx (hooke’s law)
what does F=ma tell us?
- force directly proportional to acceleration
- mass inversely proportional to acceleration
what is friction?
force that opposes motion + produces heat
what is air resistance?
friction due to movement through air.
what is the difference between mass and weight?
M: the amount of matter, kg, doesn’t change
W: force of gravitational field strength on mass, N, changes w gravity
how do you calculate weight?
mass x gravity
unit for mass
kg
how do you calculate gravity?
weight / mass
what is hooke’s law?
force is directly proportional to extension (F = kx)
what are k and x in F=kx?
k is spring constant
x is extension
what is the limit of proportionality?
- the point at which Hooke’s Law no longer applies
- graph no longer linear
what happens if we keep adding more load to a spring?
- reaches limit of proportionality and hooke’s law no longer applies
- breaks
what is the centre of mass?
where the mass of an object is concentrated
