Ignoring details associated with friction, extra forces exerted by arm and leg muscles, and other factors, we can consider a pole vault as the conversion of an athlete’s running kinetic energy to gravitational potential energy. If an athlete is to lift his body 4.8 m during a vault, what speed must he have when he plants his pole?
A sprinter of mass 60 kg accelerates from 2.00 m/s to 8.00 m/s over a 25.0-m-distance of racetrack. The sprinter is running into the wind, which exerts an average force of 30.0 N. What average force does the sprinter exert on the track?
A sled of mass 70 kg starts from rest and slides down a incline 80 m long. It then travels for 20 m horizontally before starting back up an incline. It travels 80 m along this incline before coming to rest. What is the net work done on the sled by friction?
A small object is placed at the top of a frictionless incline. The object slides downward along the incline onto a rough horizontal surface, where it comes to rest in 5.0 s after traveling 60 m.
What is the speed of the object at the bottom of the incline?
What is the object’s acceleration along the horizontal surface?
What is the height of the incline?
A girl and a skateboard have a total mass of 47 kg. The girl rides the skateboard at a horizontal speed of 13 m/s towards a ramp that is inclined at above the horizontal. The girl travels 12.5 m upward along the ramp before coming to rest. What is the magnitude of the net frictional force that acted on the skateboard along the ramp?