29. When frozen carbon dioxide (CO2) is heated, it changes directly into a gas. Which statement BEST indicates that a physical change has taken place?
a. Heat caused an increase in gas production,
b. Heat caused a new substance to form.
C. Heat caused a decrease in energy.
d. Heat caused a change in state.

Which statement best describes the superposition principle? a.) if two in-phase waves arrive simultaneously at a point, their amplitudes add up b.) if two out-of-phase waves arrive simultaneously at a point, their amplitudes add up c.) if two in-phase waves arrive at a point one after another, their amplitudes add up d.) if two out-of-phase waves arrive at a point one after another, their amplitudes adds up

Relative to the ground below, how many joules of potential energy does a 1000-kg boulder have at the top of a 5-m ledge?

Frequency of electromagnetic waves that a radio station is assigned. what do you call this type of wave?