exam Flashcards
What is a ruler used to measure
A rule (ruler) is used to measure length for distances between 1mm and 1meter
SI unit for length
SI unit for length is the meter (m)
How to find out volume of regular object
To find out volume of regular object, use mathematical formula
how to find out volume of irregular object
To find out volume of irregular object, put object into measuring
cylinder with water. When object added, it displaces water,
making water level rise. Measure this rise. This is the volume.
what is a MICROMETER SCREW GAUGE used for
Used to measure very small distances
Determination of the diameter โdโ of a wire
How to use a micrometer screw gauge
Place the wire between the anvil and spindle end as indicated in
the diagram.
Rotate the thimble until the wire is firmly held between the anvil
and the spindle.
The ratchet is provided to avoid excessive pressure on the wire. It
prevents the spindle from further movement - squashing the wire
How to take a reading on a micrometer screw gauge
First look at the main scale. This has a linear scale reading on it. The long lines are every millimetre the shorter ones
denote half a millimetre in between.
what do clocks measure
Interval of time is measured using clocks
SI unit for time
SI unit for time is the second(s)
How to find the amount of time it takes a pendulum to make a spin
To find the amount of time it takes a pendulum to make a spin,
time ~25 circles and then divide by the same number as the
number of circles.
Principle of conservation of linear momentum: when bodies in a
system interact, total momentum remains constant provided no
external force acts on the system. What is speed
Speed is the distance an object moves in a time frame. It is
measured in meters/second (m/s) or kilometers/hour (km/h).
Speed equation
๐บ๐๐๐๐ = ๐ป๐๐๐๐ ๐ซ๐๐๐๐๐๐๐/๐ป๐๐๐๐ ๐ป๐๐e
Is speed a vector or scalar quantity
Speed is a scalar quantity
how to calculate distance travelled on SPEED/TIME GRAPHS
Area under the line equals to the distance travelled
Gradient of speed/time graph
๐บ๐๐๐๐๐๐๐ก = ๐ฆ2โ๐ฆ1/๐ฅ2โ๐ฅ1
how to calculate distance travelled with constant speed
With constant speed: ๐๐๐๐๐ ร ๐๐๐e
how to calculate distance travelled with constant acceleration
With constant acceleration:
๐น๐๐๐๐ ๐๐๐๐๐+๐ผ๐๐๐ก๐๐๐ ๐๐๐๐๐ / 2 ร ๐๐๐e
Acceleration equation
๐จ๐๐๐๐๐๐๐๐๐๐๐ =
๐ญ๐๐๐๐ ๐บ๐๐๐๐ โ ๐ฐ๐๐๐๐๐๐ ๐บ๐๐๐๐ / ๐ป๐๐๐ ๐ป๐๐๐n
What is acceleration
Acceleration is the rate of change in velocity per unit of time,
measured in meters per second, or m/s2
Is acceleration a vector or scalar quantity
Acceleration is a vector quantity
what does positive acceleration mean
Positive acceleration means the velocity of a body is increasing
What does negative acceleration mean
Deceleration or negative acceleration means the velocity of a
body is decreasing
what happens if the acceleration is not constant
If acceleration is not constant, the speed/time graph will be
curved.
What is the downwards acceleration of an object caused by
The downwards acceleration of an object is caused by gravity.
This happens most when an object is in free. Objects are slowed
down by air resistance. Once air resistance is equal to the force
of gravity, the object has reached terminal velocity. This means
that it will stay at a constant velocity. acceleration of free fall for
a body near to the Earth is constant (G=10m/s)
What is mass
Mass: amount of matter an object contains, and is a property
that โresistsโ change in motion
what is weight
Weight is the force of gravity acting on an object, measured in
Newtons, and given by the formula:
Weight formula
๐พ๐๐๐๐๐ = ๐ด๐๐๐ ร ๐ฎ๐๐๐๐๐y
what can weights and masses be compared by
Weights (and hence masses) may be compared using a balance
Density equation
๐ซ๐๐๐๐๐๐ = ๐ด๐๐๐/๐ฝ๐๐๐๐e
how to work out density of a liquid
Density of a liquid: place measuring cylinder on a balance, fill
measuring cylinder with the liquid. The change in mass is mass of
liquid and volume is shown on the scale, then use formula.
How to find out density of a solid
Finding the volume: To find out volume of a regular object,
use mathematical formula. To find out volume of an irregular
object, put object into a measuring cylinder with water and
the rise of water is the volume of the object
Finding the mass: weigh object on a scale and use formula
how to work out wether something will float or sink in the water
The density of water is 1g/cm3
if an object has a greater density
than that, then it will sink in water, and if the objectโs density is
less than that, then it will float in water
What will a force produce
A force may produce a change in size and shape of a body, give an
acceleration or deceleration or a change in direction depending on
the direction of the force.
What happens when there is no resultant force acting on a body
If there is no resultant force acting on a body, it either remains at
rest or continues at constant speed in a straight line
what is friction
Friction: the force between two surfaces which impedes motion
and results in heating
What is a form of friction
Air resistance is a form of friction
what do springs extend in proportion to
Springs extend in proportion to load, as long as they are under their proportional limit.
What is limit of proportionality
Limit of proportionality: point at which load and extension are no longer proportional
what is elastic limit
Elastic limit: point at which the spring will not return to
its original shape after being stretched
Load equation
๐ฟ๐๐๐(๐) = ๐๐๐๐๐๐ ๐ถ๐๐๐ ๐ก๐๐๐ก ร ๐๐ฅ๐ก๐๐๐ ๐๐๐ ๐ญ = ๐๐
force equation
F=MA
๐ญ๐๐๐๐ = ๐ด๐๐๐ ร ๐จ๐๐๐๐๐๐๐๐๐๐๐
What is force measured in
Force is measured in Newtons
what is the amount of force needed to give 1kg an acceleration of 1m/s2
1 Newton is the amount of force needed to give 1kg an
acceleration of 1m/s2
What does an object at steady speed in circular orbit do
An object at steady speed in circular orbit is always accelerating as
its direction is changing, but it gets no closer to the center
what is centripetal force
Centripetal force is the force acting towards the center of a circle.
It is a force that is needed, not caused, by circular motion
What is centrifugal force
Centrifugal force is the force acting away from the center of a
circle. This is what makes a slingshot go outwards as you spin it.
The centrifugal force is the reaction to the centripetal force. It has
the same magnitude but opposite direction to centripetal force.
newtons first law
First law of motion: If no external for is acting on it, an object will,
if stationary, remain stationary, and if moving, keep moving at a
steady speed in the same straight line
Newtons second law
Second law of motion: ๐ญ = ๐๐
newtons third law
Third law of motion: if object A exerts a force on object B, then
object B will exert an equal but opposite force on object A
Moment equation
๐ด๐๐๐๐๐(๐ต๐) = ๐ญ๐๐๐๐(๐ต) ร ๐ซ๐๐๐๐๐๐๐ ๐๐๐๐ ๐ท๐๐๐๐(๐)
what is the clockwise and anticlockwise moment in equilibrium
In equilibrium, clockwise moment = anticlockwise moment
What does increasing force or distance from the pivot do to the moment of a force
Increasing force or distance from the pivot increases the moment
of a force
what is a lever
Levers are force magnifiers
Why is turning a bolt easier with a wrench
Turning a bolt is far easier with a wrench because distance
from pivot is massively increased, and so is the turning effect.
what is the centre of mass
Centre of mass: imaginary point in a body
where total mass of body seems to be acting
how to work out the centre of mass
Working out the center of mass:
Mark three points on the edge of the card
Make a hole using a pin on each point
Hang it on a cork board and make a line when it is stable
Do this for all three points Where all three lines intersect, this is the center of mass
when will an object be in stable equilibrium
An object will be in stable equilibrium when it returns to its
original position given a small displacement
What does an object need to start rotating
For an object to start rotating it needs to have an unbalanced
moment acting on it
what is a scalar quantity
A scalar is a quantity that only has a magnitude (so it can only be
positive) for example speed.
What is a vector quantity
A vector quantity has a direction as well as a magnitude, for
example velocity, which can be negative
linear momentum equation
Linear momentum: product of mass and velocity
๐ = ๐๐ฃ
Principle of conservation of linear momentum:
when bodies in a system interact, total momentum remains constant provided no
external force acts on the system.
๐๐ด๐ข๐ด + ๐๐ต๐ข๐ต = ๐๐ด๐ฃ๐ด + ๐๐ต๐ฃB
Impulse equation
product of force and time for which it acts
๐น๐ก = ๐๐ฃ โ ๐u
What is energy
amount of work and its measured in Joules (J)
Why may an object have energy
An object may have energy due to its motion or its position
conservation of energy
Conservation of energy: energy cannot be created or destroyed,
when work is done, energy is changed from one form to another
Energy can be stored
Kinetic energy
Due to motion
gravitational energy
From potential to fall
Chemical energy
In chemical bonds
strain energy
Compress/stretch
Nuclear energy
Atoms rearranged/split
internal energy
Motion of molecules
Electrical energy
Carried by electrons
light energy
Carried in light waves
Sound energy
Carried in sound waves
Kinetic energy equation
๐พ๐๐๐๐ก๐๐ ๐๐๐๐๐๐ฆ = 1/2 ร ๐๐๐ ๐ ร ๐๐๐๐๐๐๐กyยฒ
๐ฒ. ๐ฌ. = ๐/๐ ๐vยฒ
Gravitational potential energy equation
๐บ๐๐๐ฃ๐๐๐ก๐๐๐๐๐ ๐๐๐ก๐๐๐ก๐๐๐ ๐ธ๐๐๐๐๐ฆ = ๐๐๐ ๐ ร ๐บ๐๐๐ฃ๐๐ก๐ฆ ร ๐ป๐๐๐โ๐ก
๐ฎ.๐ท. ๐ฌ. = ๐๐h
Example of conversion of energy
A book on a shelf has gravitational potential energy, if it falls of the shelf it will have kinetic energy
describe renewable and non renewable energy
Renewable sources are not exhaustible
Non-renewable sources of energy are exhaustible
What is the source of most of our energy
The sun is the source of energy for all our energy resources except
geothermal, nuclear and tidal
how is energy made in the sun
In the sun, energy is created through a process called nuclear
fusion: hydrogen nuclei are pushed together to form helium.
What is efficiency
Efficiency: how much useful work is done with energy supplied
efficiency equation
๐ฌ๐๐๐๐๐๐๐๐๐ =๐ผ๐๐๐๐๐ ๐๐๐๐๐๐ ๐๐๐๐๐๐ / ๐ฌ๐๐๐๐๐ ๐๐๐๐๐ ร ๐๐๐%
๐ฌ๐๐๐๐๐๐๐๐๐ = ๐ผ๐๐๐๐๐ ๐๐๐๐๐ ๐๐๐๐๐๐ /๐ท๐๐๐๐ ๐๐๐๐๐ ร ๐๐๐%
What is work
Work is done whenever a force makes something move.
The unit for work is the Joule (J).
1 joule of work = force of 1 Newton moves an object by 1 meter
Work equation
๐พ๐๐๐ ๐ ๐๐๐ (๐ฑ) = ๐ญ๐๐๐๐ (๐ต) ร ๐ซ๐๐๐๐๐๐๐ (๐)
๐พ = ๐ญ๐ซ
What is power
Power is the rate of work
The unit for power is Watts (W)
Power equation
๐ท๐๐๐๐ (๐พ) = ๐พ๐๐๐ ๐ซ๐๐๐ (๐ฑ) / T๐๐๐ ๐ป๐๐๐๐ (๐)
pressure equation (solid)
๐ท๐๐๐๐๐๐๐ (๐ท๐) = F๐๐๐๐ (๐ต) / ๐จ๐๐๐ (๐๐)
๐ท = ๐ญ / ๐จ
Unit: Pascals (Pa) = N/m2
pressure equation (liquid)
๐ท๐๐๐๐๐๐๐(๐ท๐) = ๐ซ๐๐๐๐๐๐(๐๐/๐๐) ร ๐ฎ๐๐๐๐๐๐(๐/๐๐) ร ๐ฏ๐๐๐๐๐(๐) ๐ท = ๐๐๐
What is the pressure in 10m water
At a depth of 10m in water, the pressure is always 100,000 Pa
(1bar) and is constant for each further 10m.
atmospheric pressure equation
1 atm = 101.325 X 103 Pa = 101 KPa
What is a manometer
A manometer measures the
pressure difference.
The height difference shows
the excess pressure in addition
to the atmospheric pressure.
What is a barometer
Tube with vacuum at the topand mercury filling the rest.
Pressure of the air pushesdown on reservoir, forcingmercury up the tube.
Measure height of mercury
~760 mm of mercury is 1 atm
what is a solid
Fixed shape and volume Strong forces of attraction between particles Fixed pattern (lattice) Atoms vibrate but canโt change position: fixed volume and shape
What is a liquid
Fixed volume but changes shape depending on its container
Weaker attractive forces than solids
No fixed pattern, liquids take shape of their container
Particles slide past each other
what is a gas
No fixed shape or volume, gases fill up their containers
Almost no intermolecular forces
Particles far apart, and move quickly
Collide with each other and bounce in all directions
Pressure in gasses
The pressure gases exert on a container is due to the particles
colliding on the container walls.
If the volume is constant, then increasing the temperature will
increase the pressure.
brownian motion
Gas molecules move at a random motion
This is because of repeated collisions with other gas molecules
Small molecules move much faster and have higher energy than larger molecules
The small particles can help move the larger particles
Brownian motion can be seen visually in smoke
What is evaporation
It is the escape of the more energetic particles and occurs
constantly on the surface of liquids
what happens if more energetic particles escape liquid
If more energetic particles escape, liquid contains few high energy
particles and more low energy particles so average temperature
decreases.
How can evaporation be accelerated by
Evaporation can be accelerated by:
o Increasing temperature: more particles have energy to escape
o Increasing surface area: more molecules are close to the
surface
o Reduce humidity level in air: if the air is less humid, fewer
particles are condensing.
o Blow air across the surface: removes molecules before they can
return to the liquid
explain thermal expansion
Solids, liquids and gasses expand when they are heated as atoms
vibrate more and this causes them to become further apart, taking
up a greater volume.
Due to differences in molecular structure of the different states of
matter, expansion is greatest in gases, less so in liquids and lowest
in solids
Applications and consequences of thermal expansion:
Overhead cables have to be slack so that on cold days, when
they contract, they donโt snap or detach.
Gaps have to be left in bridge to allow for expansion
Bimetal thermostat: when temperature gets too high, bimetal
strip bends, to make contacts separate until temperature falls
enough, then metal strip will become straight again and
contacts touch, to maintain a steady temperature
For a fixed mass of gas at constant pressure, the volume is directly
proportional to the Kelvin temperature
How to find the fixed mass of gas at constant pressure
For a fixed mass of gas at constant pressure, the volume is directly
proportional to the Kelvin temperature
What can a physical property that varies with temperature be used for
A physical property that varies with temperature may be used for
measurement of temperature
how does a liquid-in-glass thermometer work
As temperature rises or falls, the liquid (mercury or alcohol)
expands or contracts.
Amount of expansion can be matched to temperature on a
scale.
How does a thermistor thermometer work
The probe contains a thermistor
The thermistor is a material that becomes a better electrical
conductor when the temperature rises (semi-conductor)
So when temperature increases, a higher current flows from a
battery, causing a higher reading on the meter
how does a thermocouple thermometer work
The probe contains 2 different metals joined metals to form 2
junctions.
The temperature difference causes a tiny voltage which makes a
current flow.
A greater temperature difference gives a greater current.
Thermocouple thermometers are used for high temperatures
which change rapidly and have a large range (-200Cยฐ to 1100ยฐC)
What are fixed points
Fixed points are definite temperatures at which something
happens and are used to calibrate a thermometer. For example,
melting and boiling point of water
how to calibrate a thermometer
Place thermometer in melting ice, this is 0 ยฐC.
Place thermometer in boiling water, this is 100 ยฐC
What is thermometer sensitivity
Sensitivity: change in length or volume per degree
How to increase thermometer sensitivity
To increase sensitivity:
Thinner capillary
Less dense liquid
Bigger bulb
how to increase thermometer range
Range: change the upper and lower fixed points
what is thermometer linearity and responsiveness
Linearity: change the distance between intervals
Responsiveness: how long it takes for the thermometer to react
to a change in temperature
What is melting
This is when a solid turns into a liquid.
Temperature increases thus kinetic energy in solid increases and
particles vibrate more rapidly but there is no increase in
temperature of the substance when melting because thermal
energy supplied is instead being used to break bonds between
particles of the solid thus making it into a liquid.
what is boiling point
Boiling point is the temperature at which a substance boils
What is boiling
This is when a liquid turns into a gas
Temperature increases thus kinetic energy in liquid increases and
particles vibrate more rapidly but there is no increase in
temperature of the substance when boiling because thermal
energy supplied is instead being used to break bonds between
particles of the liquid thus making it into a gas.
What is melting point
Melting point is the temperature at which a substance melts
