A car’s horn has a frequency of 1000 Hz. An observer hears the horn at a pitch of 1.10 kHz. If the speed of sound in air is 345
m/s, the speed that the car was travelling, relative to the
observer, is ___ m/s.

31.4 m/s

Explanation:

The Doppler equation describes how sound frequency depends on relative velocities:

fr = fs (c + vr)/(c + vs),

where fr is the frequency heard by the receiver,

fs is the frequency emitted at the source,

c is the speed of sound,

vr is the velocity of the receiver,

and vs is the velocity of the source.

Note: vr is positive if the receiver is moving towards the source, negative if away.

Conversely, vs is positive if the receiver is moving away from the source, and negative if towards.

Given:

fs = 1000 Hz

fr = 1100 Hz

c = 345 m/s

vr = 0 m/s

Find: vs

1100 = 1000 (345 + 0) / (345 + vs)

vs = -31.4

The speed of the car is 31.4 m/s.

the answer would be c

what experimental evidence led scientists to change from the previous model to this one?

a few of the positive particles aimed at a gold foil seemed to bounce back.

the colors of light emitted from heated atoms had very specific energies.

experiments with water vapor showed that elements combine in specific proportions.

cathode rays were bent in the same way whenever a magnet was brought near them.