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

Consider an ordinary, helium-filled party balloon with a volume of 2.2 ft3. the lifting force on the balloon due to the outside air is the net resultant of the pressure distribution exerted on the exterior surface of the balloon. using this fact, we can derive archimedes’ principle, namely that the upward force on the balloon is equal to the weight of the air displaced by the balloon. assuming that the balloon is at sea level, where the air density is 0.002377 slug/ft3, calculate the maximum weight that can be lifted by the balloon. note: the molecular weight of air is 28.8 and that of helium is 4.

If the force applied to an object remains constant, is more power needed for the object to move faster ? explain

Determine the age of a fossil if it had only one eighth of its original carbon-14 content remaining?