Energy Activity Sheet 1 Name:_______
How much work do you do?
Energy makes change possible. We use it to do things for us. It allows us to travel to school on buses and move ferries to Rottnest. It bakes a cake in the oven and keeps ice cream frozen in the freezer. It powers our mp3 players and lights our homes. Energy is needed for our bodies to grow and it allows our minds to think. The scientific definition is:
Energy is the ability to do work.
Work is defined as the transfer of energy.
To understand the concept of energy let us first get an idea of what work means in a branch of science called physics. So how much work do you do?
Experiment 1: Calculating Work
Aim: To calculate the amount of work produced by a student running up stairs.
Safety Issues: In this experiment a member of your group will need to run up a flight of stairs. Normally you should not run on stairs so to make it safe have one group member watching at the top and one watching at the bottom of the stairs to make sure there will be no-one else on the stairs. Do not run up the stairs if you are sick or have a medical problem check with the your teacher if unsure. Run up stairs never run down stairs.
Materials: 1 stopwatch
1 long tape measure or 1 long length of string (long enough to
measure height of stairs)
1 pen and paper to record results
Procedure:
1. Measure the height of the stairs. Either by a tape measure or piece of string (tie an object to a long piece of string, lower it vertically from the top of the stairs, and mark the length of the string from the floor level to the top of the stairs. Then measure the length of string).
2. One group member who knows or can guess their mass (the same of weight in earth’s gravity) is designated as runner. Another group member is the time keeper and will operate the stopwatch to time how long it takes to run up the stairs. The other members of the group monitor the stairs.
3. Make 3 attempts to run up the stairs time them and record the results.
Results:
Time: Attempt 1__________ Attempt 2__________ Attempt 3__________
Height of stairs: ________ metres(m) Mass of student: _________kilograms (kg)
Calculations:
In science we use symbols to represent words or concepts this is called scientific notation. In physics work is represented by W, m is mass, g is the strength of the Earth’s gravitational field (approximately 10 newtons per kilogram), h is the vertical distance you travelled. So to calculate how much work you did running up the stairs we use the formula.
W = mgh
W = (weight in kilograms)x(10 newtons/kg)x(distance in meters)
Example: Suppose that your mass is 40 kg, that you live on the Earth (g = 10 newtons/kg) and that you ran upstairs with a total height of 12 m, then you did an amount of work.
W = mgh = (40 kg)x(10 newtons/kg)x(12 m) = 4,800 joules.
The joule (J) is the unit in which energy is measured. It was named after the British Scientist James Prescott Joules in the nineteenth century. However, a joule is a fairly small unit. One thousand joules is a kilojoule, symbol kJ (kilo means one thousand) and is more commonly used. So, in our worked example, we’d say that this student has did 4.8 kilojoules of work or used 4.8 kilojoules of energy.
Your Calculation
So how much work did you do?
Do your calculation here.
W = mgh = (____ kg)x(10 newtons/kg)x(____ m) = ______ joules = ____ kJ.
Reflection Questions:
How much work would you do if you ran up twice as high?
Would you do more work if you carried a heavy object? Explain.
Would you do less work to run up similar stairs on the moon, where the gravitational field is weaker and your weight would be less? Explain.
Credits
Activity Sheet 1 modified with materials from Glimpses of Science (Connor,Ginges, Hatsidimitis, & Wolfe, 2010).
How much work do you do?
Energy makes change possible. We use it to do things for us. It allows us to travel to school on buses and move ferries to Rottnest. It bakes a cake in the oven and keeps ice cream frozen in the freezer. It powers our mp3 players and lights our homes. Energy is needed for our bodies to grow and it allows our minds to think. The scientific definition is:
Energy is the ability to do work.
Work is defined as the transfer of energy.
To understand the concept of energy let us first get an idea of what work means in a branch of science called physics. So how much work do you do?
Experiment 1: Calculating Work
Aim: To calculate the amount of work produced by a student running up stairs.
Safety Issues: In this experiment a member of your group will need to run up a flight of stairs. Normally you should not run on stairs so to make it safe have one group member watching at the top and one watching at the bottom of the stairs to make sure there will be no-one else on the stairs. Do not run up the stairs if you are sick or have a medical problem check with the your teacher if unsure. Run up stairs never run down stairs.
Materials: 1 stopwatch
1 long tape measure or 1 long length of string (long enough to
measure height of stairs)
1 pen and paper to record results
Procedure:
1. Measure the height of the stairs. Either by a tape measure or piece of string (tie an object to a long piece of string, lower it vertically from the top of the stairs, and mark the length of the string from the floor level to the top of the stairs. Then measure the length of string).
2. One group member who knows or can guess their mass (the same of weight in earth’s gravity) is designated as runner. Another group member is the time keeper and will operate the stopwatch to time how long it takes to run up the stairs. The other members of the group monitor the stairs.
3. Make 3 attempts to run up the stairs time them and record the results.
Results:
Time: Attempt 1__________ Attempt 2__________ Attempt 3__________
Height of stairs: ________ metres(m) Mass of student: _________kilograms (kg)
Calculations:
In science we use symbols to represent words or concepts this is called scientific notation. In physics work is represented by W, m is mass, g is the strength of the Earth’s gravitational field (approximately 10 newtons per kilogram), h is the vertical distance you travelled. So to calculate how much work you did running up the stairs we use the formula.
W = mgh
W = (weight in kilograms)x(10 newtons/kg)x(distance in meters)
Example: Suppose that your mass is 40 kg, that you live on the Earth (g = 10 newtons/kg) and that you ran upstairs with a total height of 12 m, then you did an amount of work.
W = mgh = (40 kg)x(10 newtons/kg)x(12 m) = 4,800 joules.
The joule (J) is the unit in which energy is measured. It was named after the British Scientist James Prescott Joules in the nineteenth century. However, a joule is a fairly small unit. One thousand joules is a kilojoule, symbol kJ (kilo means one thousand) and is more commonly used. So, in our worked example, we’d say that this student has did 4.8 kilojoules of work or used 4.8 kilojoules of energy.
Your Calculation
So how much work did you do?
Do your calculation here.
W = mgh = (____ kg)x(10 newtons/kg)x(____ m) = ______ joules = ____ kJ.
Reflection Questions:
How much work would you do if you ran up twice as high?
Would you do more work if you carried a heavy object? Explain.
Would you do less work to run up similar stairs on the moon, where the gravitational field is weaker and your weight would be less? Explain.
Credits
Activity Sheet 1 modified with materials from Glimpses of Science (Connor,Ginges, Hatsidimitis, & Wolfe, 2010).
| energy_activity_sheet_1.doc |
