Heko if you understand please and thanks

When an object is heated it contracts. a. true b. false

Suppose a wheel with a tire mounted on it is rotating at the constant rate of 2.15 times a second. a tack is stuck in the tire at a distance of 0.373 m from the rotation axis. noting that for every rotation the tack travels one circumference (a) find the tack's tangential speed. (b) what is the tacks radial acceleration?

The molecular weight of oxygen gas (o2) is 32 while that of hydrogen gas (h2) is 2. prove that under same physical conditions, the velocity of sound in hydrogen is four times that in oxygen