Question

A child walks due east on the deck of a ship at 4 miles per hour.
The ship is moving north at a speed of 12 miles per hour.

Find the speed and direction of the child relative to the surface of the water.

Speed = mph

The angle of the direction from the north = (radians)
i have the speed i couldn't find the direction !

Answer 1

This is just the hypotenuse of a right triangle with sides 4 and 12.

Answer 2

Hi e_godlike, been a while since I done vectors, maybe someone who has done applied math/physics knows this, but since this seems relativeley simple(i.e north and east) the direction will be northeast (using parralelogram rule) i imagine. the speed would be calculated then using pythagoras' thereom (as the resultant vector - the diagonal of parallelogram) would form a right angle triangle. from this you could also use basic trig to find angle

Answer 3

direction will be the arctangent of (4/12) or ArcTan(1/3)

Answer 4

if you are giving a bearing from North = zero degrees and degrees grow clockwise.

Answer 5

it says its wrong !

Answer 6

I get 18.43 degrees
http://www.wolframalpha.com/input/?i=arctan%281%2F3%29

Answer 7

So did I!
I think the error lies in arctan of 12/4 not 4/12 and then minus this from 90 degrees!

Answer 8

yeah but the answer is in radians ! plus when i even convert it to radians it still says its wrong !

Answer 9

If zero degrees is due East maybe.

Answer 10

got it ! i had ro round it up ! thanks so much !

Answer 11

Well done Valpey, just signed up as a fan!