A 0.50-kg mass attached to the end of a string swings in a vertical circle (radius = 2.0 m). When the mass is at the lowest point on the circle, the speed of the mass is 12 m/s. What is the magnitude of the force of the string on the mass at this position?
A) 31 N
B) 36 N
C) 41 N
D) 46 N
E) 23 N

Question

Quizplus · Accepted Answer

At the lowest point, the tension in the string provides the centripetal force necessary for the circular motion of the mass. Using the centripetal force equation, Fc = mv^2/r, where Fc is the centripetal force, m is the mass, v is the speed, and r is the radius, we can solve for the tension in the string.
Fc = mv^2/r = (0.50 kg)(12 m/s)^2/(2.0 m) = 36 N
Therefore, the magnitude of the force of the string on the mass at the lowest point is 36 N. Choice C is the correct answer.

A 050-Kg Mass Attached to the End of a String Swings