I'm not sure what equation is used on this particular problem. How much time would be requird to stop a 2,000 kg car that is moving at 80.0 km/hr if the braking force is 8,000 N? I know..... Mass 2000 kg Acceleration is 80.0 km/hr Breaking force is 8,000 N What tension must a 50.0 cm length of string support in order to whirl an attached 1,000.0 gram stone in a circular path at 5.00 m/s? I used the formula F= mv^2/ r = (1,000.0 g) (5.00 m/s)/ 50.0 cm = 1,000.0 x 5.00 g*m/s ____________________ 50.0 I wanted to know if I was tackling this question correctly..if not what am I doing wrong???? THX!