posted by help on .
The force F = (3.2, -7.1) N acts on a mass of 1.15 kg. At time t = 0 s, the mass has a velocity v0 = (-0.46, 0.36) m/s.
What is the angle (in degrees) of the initial velocity, measured counter-clockwise from the +x-axis?
I got 38.04 degrees but isn't the right answer
Since they are asking about initial conditions only, the force makes no difference
Vo,x = -0.46 m/s
Vo,y = 0.36 m/s
The Vo vector is aimed in the second quadrant, at an angle of arctan36/46 = 38 degrees to the -x axis. That would be an angle of 142 degrees from the +x axis, measured counterclockwise.