# Velocity of Raindrops: Car & Earth Reference Frames

• portillj
In summary, the car is travelling due east at a speed of 35 Km/h, while raindrops are falling at a constant speed vertically with respect to the Earth. The angle of the rain on the side windows of the car is 65 degrees with the vertical.
portillj
A car travels due east with a speed of 35.0 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 65.0° with the vertical. Find the velocity of the rain with respect to the following reference frames.
(a) the car
(b) the Earth

I tried to solve the problem by putting it in a pythagorean model... 35/cos(65) but it did not work... HELP

The angle of the rain is along the hypotenuse of the triangle, and it is 65 degrees from the vertical side of length 35. Since you want to find the length of the side opposite the angle, and you have only the adjacent side length, you need to use tan.

How would the triangle would look!? i get confused when it says 65degrees from the vertical side of length 35

portillj said:
How would the triangle would look!? i get confused when it says 65degrees from the vertical side of length 35

With these questions it's usually best to draw out a small sketch to visualise what is happening.

wat does it mean with 65 degrees from the vertical side of length 35? how does tat affect the triangle

portillj said:
wat does it mean with 65 degrees from the vertical side of length 35? how does tat affect the triangle

Draw a base line that represents the length of 35, then from that sketch a line 60 degrees from that base.

i was told to use tan to find the answer! but i don't have the opposite side? also wat's the difference btw the car and the earth

Heh, oops, may have given you a spot of bad advice there. I thought you needed to find the velocity of the car, which is what using tan would get you.

You were right with what you had before. That would tell you the resultant velocity of the rain relative to the car.

With respect to the Earth, the question has already said that the rain is falling vertically downwards at 35 Km/h, so I dunno, I guess that's just it.

i was not able to get the answer for the first one and well the Earth i got it wrong!

Portillj show us some of your working.

## 1. What is the velocity of raindrops in a car reference frame?

The velocity of raindrops in a car reference frame is highly dependent on the speed of the car. If the car is stationary, the raindrops will appear to be falling straight down with a velocity of 9.8 m/s due to gravity. However, if the car is moving, the raindrops will appear to be falling at an angle due to the combined effect of gravity and the car's velocity.

## 2. How does the velocity of raindrops in an Earth reference frame differ from that of a car reference frame?

The velocity of raindrops in an Earth reference frame is solely dependent on gravity and will always be a constant 9.8 m/s straight down. In contrast, the velocity of raindrops in a car reference frame will vary based on the car's speed and direction of travel.

## 3. Does the shape of the raindrop affect its velocity in different reference frames?

Yes, the shape of a raindrop can impact its velocity in different reference frames. For example, a flat and wide raindrop will have a higher air resistance and thus a lower terminal velocity compared to a slim and round raindrop. This can cause the raindrops to fall at different velocities in different reference frames.

## 4. How do different weather conditions affect the velocity of raindrops in a car reference frame?

Different weather conditions, such as wind and air density, can impact the velocity of raindrops in a car reference frame. Strong winds can cause the raindrops to fall at an angle, and higher air density can result in a faster terminal velocity for the raindrops. These factors can also vary depending on the direction of travel of the car.

## 5. Is there a way to measure the velocity of raindrops in different reference frames?

Yes, there are various methods to measure the velocity of raindrops in different reference frames. One way is to use a high-speed camera to capture the motion of the raindrops and then analyze the footage to determine their velocity. Another method is to use a weather balloon or other instruments to collect data on wind speed and air density, which can help estimate the velocity of raindrops in different reference frames.

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