A skier starts from rest at the top of a hill.The skier coas
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A skier starts from rest at the top of a hill.The skier coasts down the hill and up a
second hill,as the drawing illustrates.The crest of the second hill is circular,with a
radius of r=36 m.Neglect friction and air resistance.What must be the height h of
the \x0crst hill so that the skier just loses contact with the snow at the crest of the second
hill?(Hint:Here you may want to use both energy conservation and force methods as
part of your solution.In any case you should identify what forces would be directed
radially inwards when the skier is at the crest of the second hill and remember that
these are the forces that would generate the skier's centripetal acceleration.Of these forces,which would vanish if contact between the skier and the hill was lost?This force might then be set to zero in the solution.)
second hill,as the drawing illustrates.The crest of the second hill is circular,with a
radius of r=36 m.Neglect friction and air resistance.What must be the height h of
the \x0crst hill so that the skier just loses contact with the snow at the crest of the second
hill?(Hint:Here you may want to use both energy conservation and force methods as
part of your solution.In any case you should identify what forces would be directed
radially inwards when the skier is at the crest of the second hill and remember that
these are the forces that would generate the skier's centripetal acceleration.Of these forces,which would vanish if contact between the skier and the hill was lost?This force might then be set to zero in the solution.)
题目大意:滑雪者从第一个坡滑下,到第二个小坡的顶部的时候,人刚好离开雪面(即速度与小坡所在的圆相切),求第一个小坡的比第二个小坡高出h是多少?
设人在第二个小坡顶部的速度为v,
由机械能守恒有 mgh=1/2*mv²
当人在第二个小坡的顶部的时候,重力充当向心力
满足mv²/R=mg
联立两式可解得h=18m
所以第一个小坡要比第二个小坡高18米
设人在第二个小坡顶部的速度为v,
由机械能守恒有 mgh=1/2*mv²
当人在第二个小坡的顶部的时候,重力充当向心力
满足mv²/R=mg
联立两式可解得h=18m
所以第一个小坡要比第二个小坡高18米
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