What Is the Speed and Angle of Raindrops in Different Reference Frames?

AI Thread Summary
The discussion centers on determining the speed and angle of raindrops relative to the ground based on observations made while driving in different directions during a rainstorm. When driving north at 25 mph, the rain appears at a 38-degree angle from the vertical, while driving south at the same speed, the rain falls straight down. The equations of motion are applied to establish the relationship between the velocity of the rain and the observed angles. The user seeks clarification on setting up the equations for both driving scenarios and how to calculate the angle using trigonometric functions. The conversation emphasizes understanding the effects of different reference frames on the observed motion of raindrops.
RockenNS42
Messages
52
Reaction score
0

Homework Statement



While driving north at 25 during a rainstorm you notice that the rain makes an angle of 38 with the vertical. While driving back home moments later at the same speed but in the opposite direction, you see that the rain is falling straight down.
a)From these observations, determine the speed of the raindrops relative to the ground.
b)From these observations, determine the angle of the raindrops relative to the ground.


Homework Equations



V=vy+vx
V'=VR-V

Where VR is the velocity of the rain



The Attempt at a Solution



When driving north I got

V=(-vRsinθR)i + (-vRcosθR)j

Using

V'=VR-V

I get V'=VR-V(-vRsinθR-25)i + (-vRcosθR)j




Im not sure how to set it up for going south. Any suggestions?
Would it look like this? V'=0i+ (-vRcosθR)j
?
And to find θ, would i use [ v'x / v'y}tan-1?


I thinks mostly all the subscripts and whatnot that's messing me up.
Thanks in advance for any help given :)
 
Physics news on Phys.org
Think of the three reference frames in this problem of interest. At rest relative to earth, moving away from home in the car, moving towards home in the car. In each reference frame the rain will be falling at a different angle. See,



Good luck!
 

Attachments

  • rain069.jpg
    rain069.jpg
    7.4 KB · Views: 521
I multiplied the values first without the error limit. Got 19.38. rounded it off to 2 significant figures since the given data has 2 significant figures. So = 19. For error I used the above formula. It comes out about 1.48. Now my question is. Should I write the answer as 19±1.5 (rounding 1.48 to 2 significant figures) OR should I write it as 19±1. So in short, should the error have same number of significant figures as the mean value or should it have the same number of decimal places as...
Thread 'A cylinder connected to a hanging mass'
Let's declare that for the cylinder, mass = M = 10 kg Radius = R = 4 m For the wall and the floor, Friction coeff = ##\mu## = 0.5 For the hanging mass, mass = m = 11 kg First, we divide the force according to their respective plane (x and y thing, correct me if I'm wrong) and according to which, cylinder or the hanging mass, they're working on. Force on the hanging mass $$mg - T = ma$$ Force(Cylinder) on y $$N_f + f_w - Mg = 0$$ Force(Cylinder) on x $$T + f_f - N_w = Ma$$ There's also...
Back
Top