Classic rain falling on a car's window problem doubt

In summary: The vertical component is due to the Earth's gravity pulling the rain down, and the horizontal component is due to the Earth's rotation. In summary, the rain has both a vertical and horizontal component of velocity with respect to the car, and this is why the traces make an angle of 60º with the vertical.
  • #1
Calabi_Yau
35
1
A car travels due east with a speed of 50.0 km/h. Raindrops are falling at a
constant speed vertically with respect to the Earth. The traces of the rain on the
side windows of the car make an angle of 60.0° with the vertical. Find the
velocity of the rain with respect to (a) the car and (b) the Earth.

I got the right answer, I considered in (a) the x-component of v(rain) the same as the horizontal component of the car's velocity, and the by trigonometry calculated the y-component.

However, I have a doubt: If the rain has only vertical velocity relative to the car, why do the traces make an angle of 60º with the vertical? For me that must mean the rain has displacement relative to the car and thus the horizontal component of the rain's velocity relative to the car is not zero!

Could you clarify this to me?
 
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  • #2
Calabi_Yau said:
A car travels due east with a speed of 50.0 km/h. Raindrops are falling at a
constant speed vertically with respect to the Earth. The traces of the rain on the
side windows of the car make an angle of 60.0° with the vertical. Find the
velocity of the rain with respect to (a) the car and (b) the Earth.

I got the right answer, I considered in (a) the x-component of v(rain) the same as the horizontal component of the car's velocity, and the by trigonometry calculated the y-component.

However, I have a doubt: If the rain has only vertical velocity relative to the car, why do the traces make an angle of 60º with the vertical? For me that must mean the rain has displacement relative to the car and thus the horizontal component of the rain's velocity relative to the car is not zero!

Could you clarify this to me?

The answer to your question is in the problem statement: "Raindrops are falling at a
constant speed vertically with respect to the Earth" (emphasis added).
 
  • #3
The rain down not have only a vertical velocity relative to the car.

If you consider the Earth as a stationary frame of reference, the Earth has velocity zero, and the rain has only a vertical component of velocity. Assuming a level road, the car has only a horizontal component of velocity.

To go to the reference frame of the car, subtract the velocities of everything by the velocity of the car.

Then, in the car's reference frame, its own velocity is zero, the Earth's velocity is horizontal and in the backwards direction, and the velocity of the rain would have a vertical and horizontal component as you say.
 

1. What causes the sound of rain falling on a car's window?

The sound of rain falling on a car's window is caused by the raindrops hitting the surface of the glass. This creates vibrations in the glass, which our ears perceive as sound.

2. Why does the sound of rain on a car's window vary in intensity?

The intensity of the sound of rain on a car's window can vary due to several factors. These include the size and shape of the raindrops, the speed and direction of the wind, and the thickness and angle of the car's windows.

3. How does the angle of the car's window affect the sound of rain?

The angle of the car's window can affect the sound of rain in two ways. Firstly, a steeper angle can cause the raindrops to hit the window with more force, resulting in a louder sound. Secondly, a flatter angle can cause the raindrops to slide off the window more easily, resulting in a softer sound.

4. Why does rain sound different on different types of car windows?

The type of material and thickness of the car's windows can affect the sound of rain. For example, a thicker window may absorb more sound, resulting in a quieter rain sound. Additionally, different materials can vibrate and resonate differently, resulting in variations in sound.

5. Can the sound of rain on a car's window be replicated artificially?

Yes, the sound of rain falling on a car's window can be replicated artificially using various methods. These include playing recordings of rain sounds or using specialized equipment to mimic the vibrations of raindrops on a car's window.

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