T1 energy changes in a system Flashcards
equation for kinetic energy
1/2 mv ^2
½ x Mass x (Velocity)²
energy (J), mass (kg), velocity (m/s)
equation for elastic potential energy
½ k x^2
½ x Spring Constant x (Extension)²
Energy (J), Spring Constant (N/m), Extension(m)
equation for gravitational potential energy
mgh
mass x gravitational field strength x height
energy (J), mass (kg), gfs (N/kg), height (m)
define specific heat capacity of a substance
amount of energy needed to raise the temperature of 1 kilogram of a substance by 1C
state the units for specific heat capacity
J/C/Kg
joules/degree celsius/kilogram
what is the definition of power
rate at which energy is transferred (or rate at which work is done)
state 2 equations for power
power = energy transferred/time power = work done/time
energy(J), work done (J), time (s)
unit of power
watt (w)
describe the energy changes involved when a ball is thrown upwards and then returns to its starting position
upwards: KE is converted to GPE
peak: maximum GPE, zero KE
downwards: GPE is converted to KE
Two motors lift the same mass through the same height. Motor A does this in half the time of Motor B. Which dissipates the most power?
A
energy transferred is the same but the time taken is less (P=E/t)
describe the energy transfers for a bungee jumper
- falling: GPE is converted to KE of jumper
- as cord tightens, KE is converted and stored as EPE
- at lowest point, jumper’s initial GPE equals the EPE stored in the cord
explain why a bungee jumper slows down once the cord begins to stretch
- KE decreases since it is converted to EPE
- since KE is proportional to velocity^2, as KE decreases, so does velocity
give examples of chemical energy stores
food
fuel (e.g. wood, coal, petrol)
batteries
state 4 different stores of energy
kinetic energy
gravitational potential energy
elastic potential energy
chemical energy
