Q. A .45-kg ball, attached to the end of a horizontal cord, is rotated in a circle of radius 1.3m on a frictionless horizontal surface. If the cord would break when the tension in it exceeds 75 N, what is the highest speed the ball can have?
Q. Spider-Man attempts to save passengers on an out-of-control train using his web-slinging power. If the train (m = 137,000 kg) was at first travelling at 33m/s and he needs to stop it within 46 s, what is the magnitude of force he must provide?