Superman dangles his watch from a thin piece of string while he is taking off from the ground horizontally at a constant acceleration a. He notices that the string makes an angle (theta) with respect to the vertical. After 20 seconds, his speed is v=134 m/s. Estimate the angle (theta).

Question

Superman dangles his watch from a thin piece of string while he is taking off from the ground horizontally at a constant acceleration a.  He notices that the string makes an angle (theta) with respect to the vertical.  After 20 seconds, his speed is v=134 m/s.  Estimate the angle (theta).

anonymous · Answer

Use the time and final velocity to find the horizontal acceleration.
Use Newton's 2nd Law and do a vector triangle with forces.  The vertical force is mg, the horizontal force is ma (the force superman needs to exert on the watch to give it a horizontal acceleration of 'a').  $$\tan \theta = \frac{ mg }{ ma }$$  and the unknown mass of the watch cancels.

anonymous · Answer

I got 6.7 m/s^2 for the horizontal acceleration, and for theta I got 55.6 degrees but apparently that's wrong.  I calculated the acceleration as final velocity-initial velocity/time, so the acceleration, I'm assuming should be correct.  Not sure what I did wrong after that.

masumanwar · Answer

they can understand every problem they need to go through treatment to