# Tension Formula

by liuquinlin
Tags: formula, tension
 P: 173 First off, let me say wow if your in 9th grade taking AP physics C. Thats unheard of in my school. Secondly, there really is no equation for tension, as its just another force, and the cardinal equation for forces is $$\Sigma$$F=ma (or in this case, F with a t subscript for tension). I suppose your equation Tension=weight +/-mass*acceleration is correct, but again, there is no formal equation for tension. The most important thing above all else, and this can never be stressed enough, is to draw a freebody diagram to see how each force is acting on each body. Now suppose you had a system where a rope is pulling up a block of mass m with force Ft, and acceleration (a). Heres how i would write out my work if this were a test: 1)$$\Sigma$$F=ma 2)Then specify each force: Ft-Fg=ma 3)move around: Ft=ma+Fg (or you can make in mg at this point) 4)Simplify:Ft=m(a+g) Now of course, this problem gets more annoying if it involves an atwood machine, or a machine that has two masses connected by a rope over a pulley. the problem becomes an even bigger pain when the pulley is given a moment of inertia, but you can save that for later