# What will be needed in order to restore the balance if necessary?

You have a beam balance, the kind of scales that tips from one side to the other, depending on the weight on each side. On the left side lies a kilogram of ice. On the right side lies the standard kilogram. The pans are in balance.
After a while all the ice melted.
Does the balance tip to the right, to the left, or does it remain unchanged?
What will be needed in order to restore the balance if necessary?

# Jar of Flies

A scientist weighs a jar of sleeping flies. Then, he shakes the jar to wake them up. While flies are flying in a closed jar, the scientist weighs the jar again. Does the jar weigh less when the flies are flying?

# Iron-nails & Iron weights. Do they keep the balance?

You have a balance beam, the kind of scales that tips from one side to the other, depending on the weight on each side. 10 kg of the iron-nails balanced on the scales by iron weights. The balance beam submerged in water. Are the scales in balance?

# Does the balance beam tip to the right, to the left, or does it remain unchanged?

You have a balance beam, the kind of scale that tips from one side to the other, depending on the weight on each side. On each side is a beaker, half-filled with water. The sides are in balance. Now, on the left side, you submerge a Ping-Pong ball suspended by a string. On the right side, you submerge a steel ball of the same volume as the Ping-Pong ball suspended from a crane.

You may ignore the mass of the strings.

Does the balance beam tip to the right, to the left, or does it remain unchanged?

Solution.