# Help wanted

by physicsss
Tags: wanted
 P: 319 A light plane is headed due south with a speed relative to still air of 200 km/h. After 1 hour, the pilot notices that they have covered only 190 km and their direction is not south but southeast. What is the wind velocity in km/h and what angle it it north of east?
 Sci Advisor HW Helper P: 3,144 The velocity of the wind is the difference between the actual velocity of the plane and the "intended" velocity of the plane.
 P: 319 not really...in the book the intended is 240 km/h but the actual is 180 km and the answer they give is 170 k/h with an angle of 41.5 N of E.
HW Helper
P: 3,144
Help wanted

 Quote by physicsss not really...in the book the intended is 240 km/h but the actual is 180 km and the answer they give is 170 k/h with an angle of 41.5 N of E.
Remember, velocity is a vector!
 P: 319 but there's no angles given.
 Sci Advisor HW Helper P: 3,144 Due south and southeast sound like angles to me! :-)
 P: 319 i still dont get it. angle is 45 degrees?
 Sci Advisor HW Helper P: 3,144 LaTex doesn't seem to be working so I'll try this: The actual speed of the plane is 190/sqrt(2) km/h so it's actual velocity is (1, -1)*190/sqrt(2). The "intended velocity of the plane is (0, -1)*200 km/h. The difference between them is the wind velocity: (190/sqrt(2), 200 - 190/sqrt(2)) Now just divide the y component by the x component to find the tangent of the angle you're looking for. A drawing might help you see it better.
Math
Emeritus