Mechanical Energy
What does the symbol F mean
What does the symbol V stand for?
Voltage
What does the symbol ΔT mean?
Change in temperature
Energy in must always equal...
Energy out
The unit of measurement for Energy
Joule (J)
What is the acceleration due to gravity?
10 m/s2 or 10 Nkg-1
Will accept force due to gravity
In a parallel circuit each branch receives the __________ voltage
same
What is the symbol for specific heat capacity?
c
What does the right hand graph represent?
Final energy (output)
What day is the PESS 1.4 Exam
20th November
Define Work (W)
A change in energy, or
Bonus if 100 points if the energy change when forced is applied and an object moves in the direction of that force or similar
In a series circuit voltage is ________ between components
shared
What is specific heat capacity measured in?
Jkg-1°C -1
or says Joules per kilogram per degree Celsius
What is the term that describes energy entering or leaving the system
Work (W)
The Law of Conservation of Energy
Energy cannot be created or destroyed, only transferred or transformed
(Only points if whole statement made)
If Brad (50kg) climbs a 5m ladder what is his Ep?
2500J
What is the formula to calculate resistance in an electrical circuit
R = V/I
What formula would I use to solve the energy required to change the state of matter of a substance?
E =mL or Q = mL
If the Ep of a basketball is 200J and it loses 20J of thermal energy on its descent, how much Ek does it have the moment before it touches the ground?
180J
Calculate the energy efficiency of a filament light bulb which draws 100J of electrical energy and only outputs 60J of radiant energy
Define Power, give it's unit and the formula you might use in a mechanical energy question.
Power is a rate at which energy is transferred, measured in Watts. Formula is P=E/t
Components in a circuit alter the ability for electrons to flow, what is the term to describe this and what energy transformation occurs at these components.
Resistance and thermal energy
250 points per part of answer
Draw the temperature and energy changes as ice is heated to 100°C
Should draw the heating curve for water with two obvious plateaus representing latent heat, with linear relationship between temp and energy showing specific heat capacity
If a ball goes from stationary to moving what's the energy transformation?
kinetic energy (kicker) -> Kinetic energy (ball)
Bonus 100 points if answer mentions work done on system and or chemical potential energy initially involved
What is resistance measured in and draw it's symbol
Ohms Ω
Why does it feel easier to walk 250m up hill rather than climb a 6.5m ladder? Your answer must also include the formula you would use to prove your answer
Because the force required is less dues to work being spread across a greater distance. F=W/d
Why is an LED light bulb considered more energy efficient than a filament bulb?
LED bulbs use electrical energy to produce light with only small amounts lost as heat, whereas filament bulbs rely on electrical energy to heat a tungsten filament enough to glow, so lots of energy is wasted as heat in the output of light.
Half points (300) if only lifespan mentioned
Explain 3 features of an insulated coffee cup which act to minimise heat transfer
Vacuum layer preventing heat transfer through conduction (no contact of particles).
Silver internal coating, reflecting radiation back into the contents of the cup.
Lid and seal which minimise the ability for energy to be lost through convection of the air above the cup.
Draw the LOL plot for the following situation: A filament light bulb switched on at the wall
Initial E - electrical, system light bulb, Final E - Majority Radiant E some Thermal E
Will accept work being done on the room in form of thermal too, as long as input E = output E
Explain what work is being done as you stand stationary in the canteen line?
None, because there has been no change in energy, also because there is no movement and no external force applied F=0 and d=0, so because W=Fd it will be 0.
if only 'none' and not an explanation, only 100 points.
A light bulb has a power rating of 60 watts and is turned on for 2 hours. How much energy does it use in joules?
432000J
W=Pt=60W x 7200s =432000J
You are given a circuit with voltage and current measurements and an electrical energy value, how might you calculate many seconds it takes to transfer that energy?
Initially use the formula P=IV, then use that power value in the formula t = E/P to solve for time.
Using the ‘particle theory of matter’, explain the difference between water droplets and water vapour.
Water droplets can move past each other, but have less kinetic energy than the force required to fully overcome electrostatic force between them. Whereas particles in vapour move freely, spaced far apart and are moving with higher kinetic energy to overcome electrostatic forces keeping particles together.
Draw the LOL plot for the following transformation:
A ball dropping and the energy output the instant before it touches the ground, where earth is not in the system.
Initial Ep= 0, work done on system (ball only), final energy is = to work in the forms of Ek and minor ETh
Must have work done to get points
What assumptions are made if a base jumpers Ep is all converted to Ek at the bottom of the jump?
No energy losses as thermal due to air resistance, and sound and will accept friction due to components of parachute etc being deployed