Velocity of Raindrops: Car & Earth Reference Frames

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A car is moving east at 35.0 km/h while raindrops fall vertically, creating an angle of 65.0° with the vertical on the car's windows. To find the velocity of the rain relative to the car, a right triangle can be visualized, where the adjacent side is the car's speed and the angle is 65 degrees. The tangent function is suggested for calculating the opposite side, which represents the rain's horizontal velocity relative to the car. For the Earth reference frame, the rain's vertical speed is simply the constant speed at which it falls, which is 35 km/h. Clarifications on the triangle's orientation and the relationship between the car and Earth are crucial for solving the problem.
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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