**Explanation:**
As discussed in chapter 5 Section 2, to move in a circle at a constant speed
a mass is subject to a centripetal force. In the case of the red ball,
the centripetal force is provided by the tension of the string. When
the black sphere is in equilibrium the tension of the string is equal to
the weight of the black sphere. By writing this down, and using Equation
5.8, a relationship between the quantities measured by the simulation can
be found. This applet will be revisited in chapter 9 when discussing
angular momentum. |