Types of Energy
The useful energy outputted from a light bulb
Light (radiant)
Describe the energy transformation that occur in an oven
electrical -> heat + light
What is the GPE of a 20kg object that is 2m off the ground?
392J
What is the work done on an object that is pushed with a force of 100N over a distance of 5m?
500J
A engine transfers 450J of energy every 10 seconds. What is the power rating of the engine?
45W
Friction causes kinetic energy to be turned into...
heat (thermal energy)
Describe the energy transformation that occur in a hair dryer
electrical-> heat + sound
What is the kinetic energy of a 20kg object moving at 2m/s?
40J
A person does 50J of work on a box when they move it 2.5m across the floor. What force did they apply? (assume no friction)
20N
A 200W computer is run for half an hour (1800s). What amount of energy did it consume?
360 000J
The type of energy that an object gains when it is raised above the surface of the Earth
Gravitational Potential Energy
Describe the energy transformation that occur in a car in motion on flat ground
Chemical energy-> light + electrical+heat+Kinetic
What is the mass of an object with a GPE of 2000J that is at a height of 20m?
10.2kg
What does it mean for an object to be doing negative work?
The object does work to the environment. (i.e the object is losing energy to friction)
A light bulb emits 30J of useful light energy. If it takes in 100J of electrical energy what is its efficiency?
30%
The energy of an object in motion
Kinetic Energy
Describe the energy transformation that occur in a washing machine.
Electrical-> heat-> kinetic
What is the mass of an object that has a KE of 450J and a speed of 10m/s?
9kg
A rollercoaster train is at the peak of the largest hill (25m high!). What speed will the train have at the bottom of the hill? The train has a mass of 500kg.
22m/s
Another lightbulb emits 50J of heat and takes in 200J of electrical energy. What is its efficiency?
75%
The energy a stretchy material gains when it is streched
elastic potential energy
Describe the energy transformation that occur in a plane. Make sure to describe at least 4 output energies
chemical-> electrical+light+heat+sound+kinetic
What is the speed of an object that has a mass of 2kg and a KE of 169J?
13m/s
A 1500kg car approaches a very tall hill with a speed of 20m/s. How far up the hill will the car make it before coming to a rest. Assume the car is turned off and is in neutral.
20.4m
An engineer claims to have an engine that uses 100J of electrical energy and outputs 120J of useful kinetic energy. Explain what is wrong with this engine
You cannot have something that is more than 100% efficient. It violates the law of conservation of energy.