Ok i understand reference frames but how do u apply them to something like this?

A car travels due east with a speed of 55.0 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掳 with the vertical. Find the velocity of the rain with respect to the following reference frames.


EARTH:


CAR:Ok i understand reference frames but how do u apply them to something like this?
You just add the relative velocity vector. It's called a Galileo or Galilean transformation:





http://en.wikipedia.org/wiki/Galilean_tr鈥?/a>Ok i understand reference frames but how do u apply them to something like this?
The easy way to think about this is that for the Earth reference fram, you're just trying to find the velocity of the raindrops. Most physics problems are done with respect to the Earth reference frame, even though they never say it specifically. (For example, when you find the velocity of a ball, you're almost always doing it with respect to the Earth.)





One way of solving the problem is by looking at the angle that the raindrops make on the window. They make an angle of 65.0掳 with the vertical, so they make an angle of 25掳 with the horizontal. You can think of the problem as a problem of vectors. You know the velocity vector in the horizontal direction, and you want to figure out the velocity vector in the vertical direction.





You can do this by setting up a proportion. It may help to draw a right triangle. Start with two lines, horizontal and vertical. These lines represent the horizontal and vertical velocity vectors. You know the angle, so draw the hypotenuse at a 65 degree angle to the vertical, and just draw the line and connect it with the horizontal.





Now you can look at the problem as a geometry problem where you're trying to find the length of the vertical side and the hypotenuse. You're told that the length of the horizontal line is 55 and you also know all of the angles in the triangle, so you have all the information you need to solve it.





The length of the vertical is the velocity of the rain with respect to the Earth, and the length of the hypotenuse is the velocity of the rain with respect to the car. It's a little difficult to explain without being able to draw the figures and show you, but I hope this makes the problem a little bit more manageable and understandable. Good luck.

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