Asiren on the top of the police car emits sound at frequency of 823 hz. the car is approaching a bystander on a sidewalk at speed 39.5 m/s. what is the freguency the bystander hears? assume the speed of sound in air to be 340 m/s.

The bystander will hear a frequency of 931.18 Hz.

Explanation:

let V = 39.5 m/s be velocity of the police car and Fs be the frequency a siren of the police car emits. let v = 0 m/s be the velocity of the bystander and Vs = 340 m/s is the velocity of sound in air.

then, we know that the bystander has to hear a higher frequency than the one emitted and the frequency that the bystander hears is given by the doppler relation:

Fo = [(Vs)/(Vs - V)]×Fs

      = [(Vs)/(Vs - V)]×Fs

      = [(340)/(340 - 39.5)]×(823)

      = 931.18 Hz

Therefore, the bystander will hear a frequency of 931.18 Hz.

the answer is d

lies a supermassive black hole called sagittarius a*, or sgr a* for short.

answer: 802.3 kilo joules of energy represents 191.75 kilo calorie of energy.

explanation:

energy released during combustion of one mole methane = 802.3 kilo joules

if 1 kilo joule = 0.239006   kilo calorie

then ,802.3 kilo joule will be = 802.30.239006 kilo calorie

802.3 kilo joule = 191.75 kilo calorie

hence, the energy in kilo calorie is 191.75 kilo calorie.