Chapter 8: Work, Energy and Power Flashcards
What is work?
Work is the ability to transfer energy from one form to another usefully.
What are energy and work measured in?
Joules
What is the law of the conservation of energy?
Energy cannot be created or destroyed. It can only be transferred or transformed.
What equation links work, force and distance?
work (w) = force (f) x distance (d)
Why will a rocket with a maximum height of 400 not always reach it?
It is not 100% efficient due to air resistance which acts against GPE and KE.
What is GPE?
GPE, aka gravitational potential energy, is the energy stored in an object when you raise it up against the force of gravity.
What is the equation for GPE?
GPE = mass (m) x gravity (g) x height (h)
Why do you feel tired if you go up stairs?
You lose energy - chemical energy from food transforms into KE and GPE.
What is KE?
KE, aka kinetic energy, is movement energy.
What is the equation that links KE, mass and velocity?
KE= 1/2mv^2
What is the relationship between KE and GPE in a pendulum?
At the highest point the pendulum reaches, there is the max GPE and the min KE. At the lowest point, there is the max KE and the min GPE. If the experiment was 100% efficient, then max GPE would = max KE.
What should I remember when I draw sankey diagrams?
1) I need a scale
2) Wasted energy goes down/up and useful energy goes straight
3) Label every arrow
What should I remember when I interpret sankey diagrams?
Look at the scale using the graph paper
How do I work out the efficiency of energy transfers?
Efficiency = useful energy output/ total energy output (x100)
How equation links power, work and time?
power (p) = work done (w)/ time (t)
