Time 90 minutes
- The students will find the mean.
- The students will predict the actions of the can.
- The students will recognize science variables.
|Materials for each student||For each group|
|1 sticker||1 bucket of water|
|2 pop cans (cleaned and empty with tabs)||different size nails|
|1 meter long of fishing wire||-narrow|
|1 fishing swivel||-wide |
|1 standard nail|
|1 permanent marker|
Tell the story of Hero and how he made an engine which was a demonstration of Newton's third law of motion.
Make the water engine with the students.
Immerse the can in the bucket of water until the can is full.
- Tie one end of the fishing wire to the loop end of the swivel.
- Carefully lift the tab of the can that stands vertically and put the clip end of the swivel to the hole of the tab.
- Trace the bottom of the can on the piece of paper.
- From that circle, find the diameter of the circle horizontal and vertical. Make a quick reference of perpendicular. Lines need to exceed the circle.
- Place the can back on the circle. The line tells you where to place a dot. It needs to be just above the bottom. Indicate the dots with a marker. *All dots need to be the same distance above the bottom.
- Puncture the can with the standard nail on the dots then gently lay the nail down on the right side of the can. You will have a hole with a slide. *The slide must be in the same direction.
- Place a sticker above one hole.
With the wire, pull the can out of the water. Two people in the group count the number of cycles the can makes by counting the sticker. Team members cannot move from where they are standing.
Do 3 trials of each can from each group member and find the mean from all the trials, then do a classroom mean.
Tell each group to change one thing (the size of the holes, the direction of the slide, etc) to each can in the group and make observations and find the mean in each can.
What are your variables? To build a "perfect" water engine, what do you need to consider while constructing it?
Objective: To observe how objects weight changes when submerged.
Scientific concepts: Density and buoyancy
- 5 film canisters
- 8 pennies
- 2 spring scales
- rubber bands or tape
- Tape together 4 film canisters, 2 canisters on the diagonal facing up and the other 2 facing down.
- Attach a string to the group of 4 canisters.
- Add 2 pennies each to two of the canisters.
- Fill canisters with water and cap.
- Attach a string to a single canister and add the same number of pennies (4) to it, fill with water and cap it.
- Suspend both of these objects from a spring scale , keeping both objects under water.
- Pull the two groups out of the water. ( The objects should now have different weights.
- Record results and give a conclusion as to why the canisters weigh different in air, but not in water.
Make sure students note that both objects have the same weight under water.
Ask students to speculate how the two objects might feel.
The small canister is more dense than the large in water, but if they were in air the larger would be heavier.
Have students define what is different about the two canisters. The concept is that the amount of mass in a standard (unit) volume will be different for the two.
If students get stumped take the canisters out of the water so
they can see them.
Try to lead students to think about the water in the canisters. Compare the four canisters to the one.
Discuss Archimedes' Principle of Displacement.
Students will experiment with the effects of one minute half-life of pieces of paper.
#9 Connections, #1 Numbers and Operation, #10 Representation
Paper, scissors, timer, marker and two boxes per group.
- Have the students label one box decayed and one box radioactive.
- Have the students put their stack of paper in the radioactive box.
- Set the timer for one minute, after one minute remove half of the paper from the radioactive box and move it to the decayed box.
- Set the timer again and then move half the remaining paper to the decayed box.
- Once they are down to a single piece of paper, they will need to start cutting it in half every time the timer rings and putting half in the decayed box.
- Continue the process until the paper gets to small to cut and therefore is fully decayed.
The number of paper you give each group must be a power of 2 (2n) for the experiment to go easily. A one minute timer can be borrowed from the year book staff developing room if you have one. They automatically time the same amount every time you depress the button. For easy cutting, the students can fold each piece in half and then cut on the fold line.
Ask the students what the half-life of the paper is, and discuss how long different amounts of paper would take to decay completely. Ask the students how much of the material is left after 4 or 5 minutes. And how many minutes would have to pass for certain fractions or percentages of the material to be remaining. (1/8, 1/64, 1/32, 6.25%, 25%, 12.5%, 3.125%)
Did You Know?
The half-life of carbon-14, used in radiocarbon dating, is 5568 years. The half-life of plutonium-239 is 24,000 years. You can use this to generate problems for your students, both of these make a good base for problems. They are more difficult than a half-life of one minute.
Further Applications: If you have more advanced algebra students you can work with them on developing the equation for radioactive decay.