posted by Chantrell .
Show that 480 W of power is expended by a weightlifter when lifting a 60-kg barbell a vertical distance of 1.2 m in a time interval of 1.5 s.
force = weight = m g = 60*9.8 = 588 Newtons
distance = 1.2 m
potential energy gained = work done = 588*1.2 = 705.6 Joules
power = energy/time = 705.6/1.5 = 470.4 Watts
Perhaps your class is using g = 10 m/s instead of 9.8 m/s^2