Efficiency
What is "waste" energy?
Output energy that isn't useful.
What is the formula for calculating kinetic energy?
Ek=0.5mv2
What is the formula for Graviational PE?
EP=mgh
What is the law of conservation of energy?
Energy cannot be created or destroyed, only changed from one form to another or transferred.
A rock with a mass 5kg is placed on a wall 2m high, what is its Kinetic Energy?
0 J
If you were to double the speed of an object what would it do to the total Kinetic Energy?
It quadruples
How do you calulate weight?
Mass x Gravity
What energy transformations occur from a wind turbine?
Mechanical -> Electricity
Who does more Work, Person A moving a 10kg bag of cement up 1m over 2 seconds or Person B holding a 10kg bag of cement above their head for 2mins?
Person A
How would you calculate the efficiency of an electric lightbulb. Identify the energy types in the formula.
Light energy output / Electrical energy Input x 100
A 0.5 kg ball is travelling at 4 m/s. Its kinetic energy is:
4 J
Ethan trips down a cliff and lands in water with 1500J of energy if his mass is 70kg, what height did he fall from?
2.19m
If a ball falls from 10m high, at 5m high what would the ratio of PE to KE be?
50/50 or 1:1
What does it mean for work to be done in terms of energy?
The force required to move an object over a distance.
A blender uses 300 J of electrical energy and produces 210 J of useful kinetic energy in 5 seconds. What is it's efficiency?
70 %
What is the speed of an object with a weight of 28.42N and 16J of Kinetic energy?
3.3m/s
A 2kg cat jumps from 1m high table onto a shelf 2m above the table, what is its GPE?
58.8 J
Explain why a pendulum eventually stops moving, even though energy is “conserved”.
Some mechanical energy is transformed into heat and sound due to air resistance and friction at the pivot — total energy remains constant, but less remains as useful mechanical energy.
A student does 400 J of work climbing a ladder in 8 s. What power is produced?
50 W
A motor does 1500 J of useful work and wastes 500 J as heat.
What is the total input energy?
2000 J
A 0.5 kg ball falls from a height of 8 m.
Find its velocity just before impact.
12.5 m/s
A 950 kg small car is hoisted on a service lift from 0.5 m to 1.6 m.
Increase in GPE?
10,241 J
A 2 kg cart rolls down a ramp. At the top, Ep = 30 J and Ek = 0 J.
At the bottom, Ep = 5 J. Find the kinetic energy at the bottom.
25J
A 60 kg student climbs stairs 3 m high.
Work done = ?
1764 J