Unit 1 Flashcards
what is speed
the distance traveled per unit time( speed = distance/time)
what is acceleration
when the speed is changing(Change in velocity over time)
what is velocity
speed in a given direction
what is mass
the amount of matter in an object
what is weight
it is a gravitational force measured in newtons
how do you calculate weight
mass x gravitational field strength
what will the effect be in the same object on different planets
mass will be the same but weight will be different
what is density
mass/unit volume
how do you find the density of a liquid
by measuring the mass of a measuring cylinder, adding the liquid and measuring the mass again
The mass of the liquid can then be found along with density
how to find the density of irregular shaped object
by placing it in water and measuring the volume before and after
what is the density of water
1 g/cm^3
what happens if the density of the object is greater or less than the density of water
if greater, it will sink
if lesser, it will float
What is newtons first law
states that an object has constant velocity unless acted on by a resultant force
what is newtons second law
force x mass = acceleration (f=ma)
what is newtons third law
every action force has an equal and opposite reaction
what is terminal velocity
the maximum velocity reached in free fall
how does terminal velocity get reached
as objects accelerate , air resistance increases
This causes resultant force downwards to decrease
acceleration starts to decrease
there is then equal and opposite reaction so there is no resultant force
terminal velocity is reached
What is friction
the force between two surfaces which impedes motion and results in heating
features of an object moving in a circle
speed is constant but direction is always changing
means velocity is always changing
it is therefore accelerating and there must be a force perpendicular to its velocity towards the centre of the circle
what is elastic deformation
the object returns to its original shape when the load has been removed
what is plastic deformation
object does not return to original shape
what is hookes law
Force = spring constant x spring extension (force = kx)
what is the limit of proportioanality
where the force extension graph stops being linear
from then on the spring doesnt obey hookes law and leads to plastic deformation
what is the moment of a force
the measure of its turning effect
moment of a force = force x perpendicular distance
in terms of turning effect, what is the pivot point
the point which the object can rotate about
what happens if the force is applied in the same lines of the pivot(Turning effects)
the object will remain stationary
what is the principle of moments
when the sum of clockwise moments equals the sum of anti clockwise moments
what is the centre of mass
the point which all mass can be considered to act
what happens if the centre of mass is below the point of suspension of an object
it will be in stable equilibrium
example: hanging plant pot
what happens if the centre of mass is higher than the point of the suspension
it will be in unstable equilibrium
what is a vector
force with magnitude and direction
what is a scalar quantity
force with just magnitude
what is momentum
mass x velocity
what is impulse
force x time
also change in momentum
what is the principle of conservation of momentum
the total momentum before is equal to the total momentum afterwards
what is an inelastic collision and formula
when kinetic energy is lost
initial momentum (first object) + initial momentum (2nd object) = (1st mass + 2nd mass) final velocity of both objects
what is an elastic collision and formula
when kinetic energy is the same before and after
initial momentum (1st object) + initial momentum (2nd object) = final momentum (1st object) + final momentum (2nd object)
what is kinetic energy
1/2 mv^2
what is gravitational potential energy
mgh(mass x gravity x height)
how is gravitational potential energy and kinetic energy related
kinetic energy = gravitational potential energy
what is work
when a force moves something through a distance
work done is equal to energy transferred
(force x distance)
what is power
the rate at which energy is transferred or rate at which work is done
power = energy transferred/time
what is efficiency
the ratio of useful work done to the total energy supplied
efficiency = useful energy output/total energy input
what is renewable energy
energy which can be replenished as quickly as its used
examples: wind, geothermal, tidal, solar ,water waves
which energy sources do not require the sun as the original source
geothermal, nuclear and tidal
why is non renewable energy used
has large energy output and usually cheaper
what is pressure
force/area
measures in pascals
how to calculate liquid pressure
density x gravity x height
