Science Buddies: "Ask an Expert"

I am a little confued about how many magnets its asking me to buy

Hi Rose,

I read over the protocol and material section. It seems to call for magnets of three different strengths, we'll call them 1, 2, and 3. The materials section suggests buying at least 21 magnets of the two lower strengths (1 and 2) and buying 42 magnets of the highest strength (3).

neodymium magnets of same outer dimensions, but increasing strength (3 values),
Notes on sources:
available online from K&J Magnetics, http://www.kjmagnetics.com;
choose magnets with the same outside dimension, but with increasing surface field strength (e.g., part numbers D901, D91, D92);
buy at least 21 magnets of the two lower strengths, and 42 of the highest strength (used for two groups of planaria).

If you look through the procedure section, you'll see that this requirement for twice as many of the highest strength magnet as the lower strength ones is because you'll actually use the highest strength magnets for two conditions: one with the planar bisected, and one with it untreated. This means the highest strength magnets are being used in one of your controls, so while you need at least 21 of each lower strength magnet, you will need 42 of the highest strength one.

In summary, you will need at least 84 magnets:
Strength 1: 21 magnets
Strength 2: 21 magnets
Strength 3: 42 magnets

I hope this helps,
JMP