Tension Force Examples
Tension Formula
Tension Problems
Tension vs. Compression
Suspension of a pendulum bobAn object suspended by a pullyPulling a sleigh by huskies and reindeerPlucking a guitar stringStretching the musclesA swing in a playgroundElevator suspended by a cableSpring in a watchSuspension bridgeSeat belt
T = FA If a string suspends an object of mass m, then the tension is given by, T = mg Where, g is the acceleration due to gravity.
How to Find the Tension Force
Suppose a block of mass m1 is lying on a horizontal table. Mass m2 pulls m1 using a pully as shown in the figure. The two blocks move with an acceleration a. According to Newton’s second law, For m2: m2a = m2g – T For m1: m1a = T Solving for the acceleration, a = m2g/(m1+m2) By using the expression for a in the second equation above, one can obtain the following. Tension Force Equation: T = m1m2g/(m1+m2) Unit for Tension: Newton or N If m1 = m2 = m, T = mg/2 Soln.: Since a string suspends the object, the only force acting on the body is its weight. The string has to bear a tension force equal to the weight to balance it. T = mg = 12 kg x 9.81 m/s2 = 118 N Problem 2: An object of mass 8 kg is pulled by a rope over a pulley. It is accelerating upward with an acceleration of 6 m/s2. Calculate the force of tension on the rope. Soln.: Since the object is pulled upward, the tension force includes its weight and force due to its acceleration. T = mg + ma = 8 kg x 9.81 m/s2+ 8 kg x 6 m/s2 = 126.5 N
