Gravitational potential energy is what gives the thrill of looking down a giant hill as you ready to descend
The above calculation described in the
picture works through the equation Kf +
Ugf =
Ki + Ugi,where K = .5mv^2
and U = mgy.
Story Time
Spif the longboarder sits at the top of the hill looking at his oncoming conquest he speculates on the speed he is capable of achieving. Since he is doing the calculations in his head and he has some gnarly bearings that let his wheels spin with very little friction he decides to disregard friction entirely from his calculations. Air resistance isn't a subject Spif has studied so it doesn't even cross his mind to include it into his calculations.
Knowing that he himself weighs about 95kg and that his sturdy board weighs a hefty 5kg he finds that in his system his mass is equivalent to 100kg. Thankfully since his father is a road surveyor he knows for a fact that this hill is 50m long and that it drops 50m over that time period.
Story Time
Spif the longboarder sits at the top of the hill looking at his oncoming conquest he speculates on the speed he is capable of achieving. Since he is doing the calculations in his head and he has some gnarly bearings that let his wheels spin with very little friction he decides to disregard friction entirely from his calculations. Air resistance isn't a subject Spif has studied so it doesn't even cross his mind to include it into his calculations.
Knowing that he himself weighs about 95kg and that his sturdy board weighs a hefty 5kg he finds that in his system his mass is equivalent to 100kg. Thankfully since his father is a road surveyor he knows for a fact that this hill is 50m long and that it drops 50m over that time period.
With this knowledge in his head he starts to
descend the hill as he continues his calculations. Ui
= 100kg*9.8m/s*50m = 49,000
which seems like quite a bit of energy in his mind. He
begins to rethink some life decisions but his increasing
speed makes him focus on the calculations at hand. Knowing Ki
= 0 due to the fact that he wasn't moving at the top of the
hill he realizes that his final kinetic energy is the same
as his initial potential energy which make his calculations
conveniently easy.
49,000 = .5*100kg*v^2 which leads him to the conclusion that v^2 = 980 and v = 31.31 m/s which is far faster than he had anticipated going.
In an unfortunate turn of events a large semi truck towing a shipment of natural gas pulls out 75m from the bottom of the hill and spontaneously explodes.
Spif begins regretting coming into this alternate dimension where friction doesn't affect his system. He decides to bring friction into his equations so as to save himself from a fiery death. Continue the story?
49,000 = .5*100kg*v^2 which leads him to the conclusion that v^2 = 980 and v = 31.31 m/s which is far faster than he had anticipated going.
In an unfortunate turn of events a large semi truck towing a shipment of natural gas pulls out 75m from the bottom of the hill and spontaneously explodes.
Spif begins regretting coming into this alternate dimension where friction doesn't affect his system. He decides to bring friction into his equations so as to save himself from a fiery death. Continue the story?