physics topic 8 - energy, forces doing work

Question 1

what is the equation for power?

Answer 1

P = E (energy transfered) / T (time taken)

or

P = W (work done) / T (time)

Question 2

what are energy, work done and Time measured in?

Answer 2

power = watts
energy / work done = Joules
Time = seconds

Question 3

name 3 ways energy can be stored

Answer 3

GPE
Elastic
thermal
kinetic
chemical

Question 4

energy transfers in a closed and open system

Answer 4

System - collection of matter

when the system changes energy is transfered either between objects or diffrent forms.

open system - matter can exchange energy with anything outside of the system. this means an open system can gain or lose energy.

closed system - cant gain or lose energy interacting with outside world.

Question 5

diffrent ways that energy of a system can be changed

Answer 5

1. electrically (like a kettle) is done when current flows
2. work done - mechanical - using force to move an object, like kicking a ball. chemical energy is taken from your leg and put into the kinetic energy store of the ball.

Question 6

work done =

Answer 6

Force (N) x distance moved in the direction of the force

E = F x D

Question 7

equation for change in GPE =

Answer 7

mass x gravity x change in height

Question 8

equation for kinetic energy =

Answer 8

KE = 1/2 mass x volume 2

Question 9

power =

Answer 9

rate at which energy is transfered

Question 10

what is 1 watt = to in joules / s

Answer 10

1 watt = 1 joule / second

Question 11

efficiency =

Answer 11

useful energy transfered by device / total energy supplied to the device