Physics Flashcards
What is the definition of temperature
how fast the speed of molecules move that make up an object
What does the specific heat capacity of a material tell us
how much heat energy needs to be added or removed to change 1 kg of the material by 1 C
What is the equation for heat energy transferred
mass x specific heat capacity x change in temperature
What is the triangle for heat energy transferred
Heat energy transferred on the top and everyting else on the bottom
The specific heat capacity of water is J/kg/°C. How much energy is needed to heat 3 kg of water from 20°C to 40°C?
4200 x 3 x (40-20)=252000
What is internal energy
the total energy stored by the particles making up a substance or system
What are the 2 parts to internal energy
kinetic energy stores and potential energy stores
What consists in potential energy stores
gravitational,elastic energy
What is the kinetic energy store
the movement energy of particles
What energy store is used when you heat up a substance
the kinetic energy store increases
What is temp
a measure of the average internal energy in a substance
How much energy does it take to increase the temp of 1kg of mercury by 1 C
139
If you were to measure the temp change what are precautions to take and why
add a lid to the liquid and insulate it well,this is so energy isn’t lost to the surroundings
What is acceleration
the rate of change in velocity
What is the first equation for acceleration
change in velocity/time
What is the second equation for velocity
Final velocity-intial velocity/time
Calculate the velocity if a car accelerates from 15 m/s to 35 m/s in 5 seconds
Final velocity-initial velocity/time
35-15/5=4
What is the third equation for velocity
2as=v sq -u sq
a=acceleration
s=distance
v=velocity
u=initial velocity
A ball is dropped from an unknown height from above the ground the ball is moving at 7 m/s.Calculate the height from which the ball is dropped
final velocity=7
initial velocity=0
anything dropped accelerates at 9.8 m/s because of gravity
acceleration=9.8 m/s
distance=7 sq- 0 sq/2(9.8)
=49/19.6=2.5
s=2.5m
What is a typical walking speed
1.5 m/s
What quantity is the rate of change of velocity?
acceleration
How is speed found from a distance time graph
it is equal to the gradient
How is velocity found from a velocity-time graph?
Velocity is read from the vertical (y) axis of a velocity-time graph.
How is acceleration found from a velocity-time graph?
Acceleration is found from the gradient of a velocity-time graph.
What is the acceleration of a horse that accelerates from rest to 4 m/s in 8 seconds?
0.5 m/s
What is the unit of acceleration?
m/s sq
What is a typical acceleration for a family car?
3 m/s sq
What is the average speed of a runner that travels 200 m in 40 seconds?
5 m/s
How is distance travelled found from a velocity-time graph?
Distance travelled is found from the area beneath a velocity-time graph.
how do you calculate resistance
voltage/current
What happens when you combine resistors in series
The total resistance always increases.
What is the rule of combining resistors in a series
the total voltage (or potential difference) across all the resistors is equal to the sum of the voltages across each resistor.
What happens when you combine resistors in parrallel
The total resistance decreases and is always less than the smallest individual resistor.
What is the equation for voltage
V=IR
Voltage=current x resistance
What is the relationship between voltage and current
as one of them increases so will the other
In a voltage graph name a reason for the line being straight
because in voltage graphs they are only straight if it is a wire or resistor
What would happen to the straightness of the line if we use a smaller or bigger resistor
it if is bigger the line will get deeper if it is smaller the line will get steeper
How do filament lamps graph works
as the current flows through it the wire heats up until it’s so hot it makes light so this increases the resistance so the curve gets less steep this shows that less current can flow per unit of potential difference because temp and resistance is so much higher
How do diode graphs work
diodes can only flow in one direction this happens because they have a really high resistance in a reverse direction so it’s impossible for current to flow
Name 6 examples of scalar quantities
Mass,temp,speed,energy,distance and time
T or F scalar quantities have magnitude only
true
T or F scalar quantities do not have a direction
true
Give 6 examples of vector qualities
Displacement,weight,force,velocity,acceleration,momentum
What do vector qualities have that scalar quantities don’t
they have magnitude and direction
What do scalar quantites tell us
imagine you were trying to get from point a to point b a scalar quantity would only tell you the distance between them
What is displacement
a distance in a specific direction
When saying displacement what do you have to include
the magnitude(500m) and distance(west)
What is a physical quantity?
something that can be measured
What does “magnitude” mean
the size of a numerical value
What is a scalar quantity?
A physical quantity that has magnitude only
T or F speed is a scalar quantity
true
How are vectors added using a scale diagram?
Vectors are added by drawing them tip-to-tail. The overall path from start to finish is the resultant of the vectors.
What is a free body diagram
a diagram that shows all the forces acting on an object
Label a free body diagram of a plane if it was going in the direction east
east-thrust
south-weight(gravity)
west-air resistance
north-lift
T or F all forces are vectors
true
What is a resultant force
the overall force on an object
How do we obtain the resultant force
on the free body diagram some of the forces will cancel each other out and then what we have left is the resultant force
What is the method for calculating the resultant force in a free body diagram
subtract the vertical forces from each other(north-south) and then the horizaontal forces from each other(east and west)and add the results up
What do we call it if we get zero when calulating the resultant force
an equilibrium
What is a force
a push or pull movement that acts on an object due to the interaction with another object
What quantity is a force and why
it is a vector quantity because they have both magnitude and direction
What is the definition of a resultant force
a single force that has the same effect as all of the original forces acting together
What does altitude mean
the height above the ground
What is the particle theory of solid
it has strong forces of attraction,and holds particles together in a fixed position
What happens to the bonds in solids when the temp increases
the forces start to weaken and they melt
What is the particle theory of liquid
weaker forces of attraction so particles can move around more freely,they have a definite volume as they are a little bit compact
what happens to the bonds in liquids when temp increases
the particles gain more energy so the particles move around faster which weakens the bonds when boiling point is reached the particles break the bonds altogether
What is the particle theory for gas
they have a weak force of attraction so the particles are free to move around,they don’t keep a definite shape or volume and will always fill a container
What motion does gas particles move in
straight lines
What happens to the bonds in gas when temp is increased
particles gain more energy so depending their enviroment they either expand or if the container is fixed the pressure will increase
What happens to gas when we decrease the temp
the particles won’t have enough energy to overcome the forces and bonds will start to form
What is the order of density for the states of matter in a closed system
solids will have the highest density,liquid the middle denisty,and gases having the lowest temp
In a closed system what dosen’t change
the mass
What are 2 ways of reducing unwanted energy transfers
by using thermal insulation and lubrication
What are the methods for allowing our home to not lose heat to the outside enviroment
1.making sure our home is sealed close(no air loss)otherwise we would lose heat by convection
2.Reduce heat loss by conduction(through solids)this is by having thick walls
How do cavity walls help preventing heat loss and how is it adapted
because of the air gap it has it reduces conduction,but because of an air gap this allows heat to be lost due to convection to solve this inbetween the air gap is insulating foam
How does insulating foam prevent heat loss
it is filled with lots of isolated air bubbles this makes it not allow any convection or conduction
How do single/double glazed windows work with heat
single glazed only have one panel so heat is easily lost by conduction
in double glazed there are 2 layers of glass with a tiny air gap which reduces conduction
What is the definition of friction
the resistance that one object encounters when moving over a solid or through a fluid
What is the problem with friction in terms of heat
it reduces the efficiency of energy transfer ad can cause it to heat up
what is the main part of the house heat is lost from and why and how is this prevented
the roof this is because hot air rises this is prevented by putting loft insulation inside the roof
What is loft insulation
it is made of fibre glass this traps lots of air this is effective as air is a very bad conductor of heat and this is efficient as convection won’t be able to form and it will also massively reduce conduction
