a bell is hanging by a string from your review mirror in the car.while you are accelerating from a stoplight to 28m/s in 6s, what angle does the string make with the vertical?
(the bell only feel the car's acceleration through the tension in the string.)
3 answers

Draw a free body diagram. The horizontal component of the string tension force provides the acceleration (28/6 = 4.667 m/s^2) , and the vertical component supports the weight.
The mass will cancel out when you get the tangent of the angle of the string, so you do not need to know it.

how do i find the vertical component?
weight=mg but i don't know what m is.

As I already stated, it is the ratio of ma to mg that gives you the tangent of the angle. The mass cancels out. So does the tension, T
T sin theta = ma
T cos theta = mg
(sin theta)/(cos theta) = tan theta = a/g
