A string 1 m long is used to whirl a 100 grams stone in a horizontal circle at a speed of 2 m/s. Find the tension in the string.

Solution

Theory:  When a body is moving in circle, it is continuously acted upon by the centripetal force directed towards the center of the circle. This force keeps the body on its circular trajectory preventing it from moving away from the circular path in a straight line. In the given problem, the centripetal force is provided by the tension in the string. Therefore, T = F_c.

Similarly, radius of the circle is equal to the length of the string.

Given                 Length of the string = radius = r = 1 m

                              Mass of the stone = 100 g = 0.1 Kg

                              Velocity of the stone = v = 2 ms^-1

Required         Tension in the string = T = ?

Now we know that centripetal force = F_c =

Put the values of m, v and r