I was doing some practice problems on physics classroom website and this is one I think is wrong.(adsbygoogle = window.adsbygoogle || []).push({});

A plane flies northwest out of O'Hare Airport in Chicago at a speed of 400 km/hr in a direction of 150 degrees (i.e., 30 degrees north of west). The Canadian border is located a distance of 1500 km due north of Chicago. The plane will cross into Canada after approximately ____ hours.

And the answer they gave is....

The plane has both a northward and a westward motion. The northward motion towards the Canadian border is dependent upon the component of velocity in the northern direction. To solve this problem, the northern component of the plane's velocity must first be determined.

vNorth = 400 • sine (150 degrees) = 200 km/hr

Once determined, the d = v • t equation can be used to determine the time that it takes the plane to reach the Canadian border.

dNorth = vNorth • t t = dNorth / vNorth = (1500 km) / (200 km/hr) = 7.5 hr

But wouldn't the component of velocity that the sine function calculated be the westward motion? Sine is opposite over hypotenuse, so the opposite would be the westward motion. The northward motion would be the adjacent, right? I'm probably wrong about the answer, but I don't know why they got the answer they did.

Thanks.

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# Homework Help: Perpendicular components of motion

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