The coefficient of dynamic friction between the grass and a 200 kg football blocking sled is 0.20. If a 100 kg football player only pushes horizontally against the sled, how large must the horizontal force be to keep the sled moving at constant velocity?

If a clock aboard a space ship traveling at 0.900 c of the speed of light relative to earth chimes once at the beginning of the hour and again when it reads one hour later, how much time would an observer on earth say elapsed between the two chimes?

Acar of mass m goes around a banked curve of radius r with speed v. if the road is frictionless due to ice, the car can still negotiate the curve if the horizontal component of the normal force on the car from the road is equal in magnitude to 101) a) mv2/r b) mg/2. d) mg e) tan[v2/(eg)]

If steel is more dense that lake water, why can a boat float