Question

1. I drag a mass m = 21 kg  in a straight line, along a horizontal surface, a distance D=23 m . I drag it at constant speed v = 0.90 m.s^−1  in a straight line using a horizontal force. The coefficients of friction are μs​ = 1.2 and μk​ = 1.1. How much work do I do? W = _____  J . ( Retain accurate values until the final calculation, but remember significant figures. )

2. A rubber band has mass m = 0.30 g  and a spring constant k = 15 N.m^−1 . I stretch it by 5.0 cm  (which in this case doubles its length). Assume the rubber band behaves as a Hooke's law spring. Assume that, when you launch the rubber band, all of the stored potential energy is converted into kinetic energy. How fast is it at the launch?

v= _____  m.s^−1

Answer 1