An Object Attached to the End of a String Swings

Multiple Choice

An object attached to the end of a string swings in a vertical circle (R = 1.2 m) , as shown. At an instant when θ = 30°, the speed of the object is 5.1 m/s and the tension in the string has a magnitude of 20 N. What is the mass of the object?

A) 2.0 kg
B) 1.5 kg
C) 1.8 kg
D) 1.2 kg
E) 0.80 kg