A 2.0-kg mass swings at the end of a light string (length = 3.0 m). Its speed at the lowest point on its circular path is 6.0 m/s. What is its kinetic energy at an instant when the string makes an angle of 50° with the vertical?
1) 21 J
2) 15 J
3) 28 J
4) 36 J
5) 23 J
Answer: 2