During takeoff, an airplane climbs with a speed of 300 m/s at an angle of 36 degrees above the horizontal. The speed and direction of the airplane constitute a vector quantity known as the velocity. The sun is shining directly overhead. How fast is the shadow of the plane moving along the ground? (That is, what is the magnitude of the horizontal component of the plane's velocity?)

Answer 1

consider what would happen if the plane were flying horizontally. The shadow would be moving exactly as fast as the plane.

What if the plane were flying vertically? Shadow would not move.

So, it's easy to see that if the plane is rising at an angle θ, the horizontal speed is 300 cosθ