The helicopter is moving horizontally at a constant velocity

[ladyazpy]

The helicopter is moving horizontally to the right at a constant velocity. The weight of the helicopter is W= 53800 N. The lift force L is generated by rotating blade makes an angle of 21.0 degrees with respect to the vertical.

a. What is the magnitude of the lift force?

b. Determine the magnitude of the air resistance R that opposes the motion

Here are the equations that I composed:

L sin (theta) - R = 0
L cos (theta) - W = 0

The answers are L = 57600 N and R = 20600 N, but I can't get these from my calculator.

Thank you.

 

[mark07]

Your equations are correct with \(\displaystyle \theta = 21^\circ\), if we put magnitudes around the vectors L, W, R to be mathematically correct.

Start with the second equation:

\(\displaystyle \L |L| = \frac{|W|}{\cos {21^\circ}} = 53800 / ( \cos {21^\circ} )\)

You get the answer approximately when you enter it in your calculator as above. Make sure your calculator is in the degrees mode.

Now take that answer and use it in the first equation to get |R|:

\(\displaystyle \L |R| = |L| \sin {21^\circ} = ?\)