How Far Downstream Will the Swimmer End Up?

AI Thread Summary
The discussion focuses on calculating how far downstream a swimmer will end up when crossing a river with a current. The river current is 22 m/s south, and the swimmer's speed is 47 m/s at an angle of 7.5 degrees south of east. By combining the swimmer's and current's velocities, a resultant speed of 54.433 m/s at an angle of 31.122 degrees south of east is determined. Given the river's width of 325 meters, the swimmer is projected to end up 196 meters downstream upon reaching the opposite bank. The calculations are confirmed, though the poster invites others to verify the results.
thegame
Messages
32
Reaction score
0
river current = 22 m/s [South]
width of the river from one side to the other = 325m
speed of person swiming = 47 m/s



if the person travels 47 m/s [E 7.5 degrees S] then how far up or down the stream will he end up when he reaches the other side?
 
Physics news on Phys.org
alright! i just did a ton of these!

first, find the vector V(current)+V(swimmer)
if you draw it, you get a triange with one leg 47, another 22, and the angle between them 97.5

then solve for the hypotnuse (c^2=a^2+b^2-2ab cos C), which gives you the magnitude of 54.433

use the same equation to get the angle formed by the hypotnuse and the swimmer. this is 23.622 degrees.

since the swimmer is at a 7.5 degree angle, add this to 23.622,
31.122

now you draw the river. from one side to the other is 325 m. now draw a line [E 31.122 S] and use inverse tan to get the answer,
196 m down

someone may want to double check. i might have done something stupid, or even did it wrong all together. haha.
 
After trying it a few times, I got 196m too..
 
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