Two trains on separate tracks move toward each other. Train 1 has a speed of 145 km/h; train 2, a speed of 72.0 km/h. Train 2 blows its horn, emitting a frequency of 500 Hz. What is the frequency heard by the engineer on train 1

Therefore,

The frequency heard by the engineer on train 1

Explanation:

Given:

Two trains on separate tracks move toward each other

For Train 1 Velocity of the observer,

For Train 2 Velocity of the Source,

Frequency of Source,

To Find:

Frequency of Observer,

 (frequency heard by the engineer on train 1)

Solution:

Here we can use the Doppler effect equation to calculate both the velocity of the source and observer , the original frequency of the sound waves and the observed frequency of the sound waves ,

The Equation is

Where,

v = velocity of sound in air = 343 m/s

Substituting the values we get

Therefore,

The frequency heard by the engineer on train 1

answer: 2×10^-2kg

explanation: density= mass per volume

vol=mass/density

converting to s.i units we have;

3÷1000kg = 0.003

1.5÷100m = 0.15

0.003/0.15 = 0.02kg