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honeybomb

Joined: 16 Oct 2013
Posts: 1
Location: United States

 Posted: Wed Oct 16, 2013 1:50 am    Post subject: Question on Friction Im learning about kinetic energy and potential energy. If I throw a ball up in e air, and there is friction present, the kinetic energy will decrease as the ball returns to the ground. What about at the top of the rise- will potential energy decrease because of the friction too? It confused me because potential energy is mass+gravity+height..... Can that be decreased based upon friction? Thanks.
hepcj
Site Admin

Joined: 23 Jun 2007
Posts: 125

 Posted: Wed Oct 23, 2013 12:31 am    Post subject: First, consider the case where there is no friction. As the ball is thrown vertically into the air from the ground there is only kinetic energy. This changes to being totally potential energy at the top of the ball's trajectory. The sum of kinetic energy + potential energy is the same throughout the flight of the ball. As one decreases the other increases. That is for no friction. Air resistance will take away some of the kinetic energy of the ball as it travels and turn it into heat but at the top of the ball's flight path there will be no kinetic energy and just potential energy. The ball would not go as high because some of the energy has gone into heating up the ball and the surroundings.
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