T4 Revision Deck Flashcards
State the equation for GPE
GPE = mgh
State the equation for KE
KE = 1/2 mv^2
State the equation for PE
PE = 1/2 kx^2
State the equation for efficiency
Eff = Usefull output / total input * 100
What does work done mean in physics?
In physics energy is defined as the ability to do work. So work is done whenever energy is transferred. (Work done = energy transferred)
State the equation for work done
Work done = force applied (N) * distance moved (m)
Define power
Power is defined as the rate of doing work. It tells you how quickly or slowly energy is transferred.
What is power measured in? What does it mean?
Watts
One watt means one joule of energy is transferred every second.
100 watts means 100 joules of energy is transferred every second.
State the equation (1) for power
Power = energy / time
State the equation (2) for power
Power = workdone / time
How many watts in a kilowatt?
1000
What is a kilowatt?
kWh stands for kilowatt hour (kWh) – it’s the way we measure energy in the home. 1 kilowatt hour is the amount of energy it takes to run a 1,000 watt (or 1kWh) appliance for 1 hour.
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Energy (in joules)=Power (in watts)×Time (in seconds)
stair practical
Measure the persons mass in kg using bathroom scales.
Convert it to weight using W = mg. This equals the upward force that will move up the stairs.
Measure the height of 1 step using the 50 cm rule. Record in m in a suitable table. Repeat for two more steps and calculate the average height in m.
Count the number of steps and record.
Calculate the vertical height = number of steps x average height of 1 step.
Calculate the work done = force x vertical height.
Time the person running the stairs. Record in the table. After a rest repeat the experiment and calculate average time.
Calculate the persons average power using: power = work done/ time taken
How many joules are in a MJ?
1,000,000 Joules
