You Do 174 J of Work While Pulling Your Sister

Multiple Choice

You do 174 J of work while pulling your sister back on a swing,whose chain is 5.10 m long.You start with the swing hanging vertically and pull it until the chain makes an angle of 32.0° with the vertical with your sister is at rest.What is your sister's mass,assuming negligible friction?

A) 22.9 kg
B) 19.5 kg
C) 26.3 kg
D) 28.4 kg