Because of the doppler effect, the sound heard by an observer listening to a moving ambulance siren, compared to what the observer would have heard if the observer and siren were both at

a. will have a lower frequency if the ambulance siren is moving towards the observer
b. will have a higher frequency if the ambulance siren is moving away from the observer.
c. will have a higher frequency if the ambulance siren is moving towards the observer.
d. will have a lower pitch if the ambulance siren is moving towards the observer.
e. will have a longer wavelength if the ambulance siren is moving towards the observer.

Acylinder with a movable piston contains 11.7 moles of a monatomic ideal gas at a pressure of 1.32×10^5 pa. the gas is initially at a temperature of 300 k. an electric heater adds 43200 j of energy into the gas while the piston moves in such a way that the pressure remains constant. cp=20.79 j k^−1 mol^−1 for a monatomic ideal gas, and that the number of gas molecules is equal to avogadro's number (6.022×10^23) times the number of moles of the gas. (a) what is the temperature of the gas after the energy is added? (b) what is the change in volume of the gas? (c) how much work is done by the gas during this process?

The force it would take to accelerate an 900-kg car at the rate of 6m/s2

Does heating a metal wire increase or decrease its electrical resistance? why?