The change in pitch of a train's horn as it passes while you are standing still can be explained by
a. sympathetic vibration.
b. ultrasonic vibrations.
c. resonance.
d. the doppler effect.

If a refrigerator is a heat pump that follows the first law of thermodynamics, how much heat was removed from food inside of the refrigerator if it released 380j of energy to the room?

What are similarities and differences between refraction, reflection, diffraction and absorption?

Photoelectrons with a maximum speed of 6.50 x 107 m/s are ejected from a surface in the presence of light with a frequency of 6.75 x 1014hz. if the mass of an electron is 9.10 x 10-31 kg, calculate in joules the maximum kinetic energy of a single electron. 3.84 x 10-15 j 1.92 x 10-15 j 5.92 x 10-23 j 3.07 x 10-16 j