In which of the following situations has work been done? select one: a. a weightlifter holds a 50kg barbell over his head for 3 minutes. b. a yoga instructor holds a handstand for 1 minute. c. a man pulls against a stationary fire truck for 5 minutes. d. a child pushes a 2kg toy 10m across the floor.

Anonzero net force acts on a particle and does work. which one of the following statements is true? the kinetic energy of the particle changes, but the speed of the particle does not change. the kinetic energy of the particle does not change, but the speed of the particle does change. the kinetic energy of the particle changes, but the velocity of the particle does not change. the kinetic energy and the speed of the particle change, but the velocity of the particle does not change. the kinetic energy, speed, and velocity of the particle change.