To determine the wavelength of sound heard by a stationary observer as a car approaches, we can use the formula:
wavelength = speed of sound / frequency
Given: Speed of sound in air = 330 m/s Frequency of the sound made by the car = 780 Hz
Let's calculate the wavelength:
wavelength = 330 m/s / 780 Hz
Now, let's convert the car's speed from km/h to m/s:
Car's speed = 100 km/h = (100 km/h) × (1000 m/km) / (3600 s/h) = 27.78 m/s
Since the car is moving towards the observer, the effective speed of sound for the observer would be the sum of the speed of sound and the car's speed:
Effective speed of sound = speed of sound + car's speed = 330 m/s + 27.78 m/s = 357.78 m/s
Now, let's calculate the updated wavelength:
wavelength = 357.78 m/s / 780 Hz
The wavelength of sound heard by the stationary observer as the car drives towards him is approximately 0.459 m (rounded to three decimal places). The unit is meters (m).