Velocity of Raindrops: Car & Earth Reference Frames

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Homework Help Overview

The problem involves analyzing the velocity of raindrops as observed from two different reference frames: a car moving due east and the Earth. The scenario includes a car traveling at 35.0 km/h and raindrops falling vertically, with the angle of the rain's trace on the car's windows given as 65.0° from the vertical.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants discuss the use of trigonometric functions to resolve the components of the rain's velocity. There are questions about the correct interpretation of the angle and how to visualize the triangle formed by the velocities. Some participants express confusion about the relationship between the angle and the sides of the triangle.

Discussion Status

The discussion is ongoing, with participants attempting to clarify the geometric representation of the problem and the application of trigonometric functions. Some guidance has been offered regarding the use of tangent to find the opposite side, but there is no consensus on the correct approach or final answer yet.

Contextual Notes

Participants are grappling with the definitions and relationships between the velocities of the rain relative to both the car and the Earth. There is an emphasis on the need for a clear visual representation to aid understanding.

portillj
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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
 
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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.

tan = opposite / adjacent.
 
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!
 
  • #10
Portillj show us some of your working.
 

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