posted by Brice .
Your friend's 11.1g tassel hangs on a string from his rear-view mirror. When he accelerates from a stop light, the tassel deflects backward toward the rear of the car. If the tassel hangs at an angle of 6.89deg relative to the vertical, what is the acceleration of the car?
From the ratio of horizontal to vertical forces on the tassel:
M*a = M*g tan6.89
M cancels out.
Solve for a.