7. Which phase changes require a gain of energy (heat)? a. melting and freezing
b. sublimation and vaporization
c. vaporization and condensation
d. sublimation and deposition

What challenges did you encounter during the circuit training program?

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?

Suppose a wire with a current is pushed upward by a magnetic field. how would the wire move if the direction of the current reversed? explain your answer.