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looping the loop

圖片參考:http://imgcld.yimg.com/8/n/HA06578099/o/7010060100...

If a ball on a track is given an initial speed u, is it true that once it can pass through the highest point, the ball can absolutely complete the circular motion?

Is it possible for the below events to occur?

圖片參考:http://imgcld.yimg.com/8/n/HA06578099/o/7010060100...

更新:

neglect air resistance and friction

2 個解答

評分
  • 10 年前
    最愛解答

    No,.(Very Connfirmed)

    In the Diagram2, The ball fell off from the track after passing through the highest point.

    This will not be happen.

    The ball will fall down if the speed of the ball is zero.

    Let the point P be the point of the ball fall down in the diagram2.

    Let P.E = potential Energy

    Let K.E = Kinetic Energy

    Since energy is consereved.

    So P.E at the highest point > P.E at P

    The loss of P.E will change to K.E.

    So the speed of the ball is increasing, so if the ball will not fall down from the highest

    point or before.

    The ball will not fall down at the rest of the loop, since the velocity of the ball will not be

    zero.

    This is a much complicated solving: You may Ignored it.

    The ball will also left the loop and move inside the , if the contripetal force is larger than the required one.

    At the highest point. The reaction force (R) given by the track to the ball will be zero and

    the only force act on the ball will only be its weight. The weight will be the centripetal force of the ball.

    After passing through the highest point, there will be a reaction force (R) act on the ball

    again.Since the weight is always pointing downward not to the centre of the loop. So the

    centripetal force cause by the weight will be decrease depends on the postion of the ball.

    The (R) will then also depends on the position to provide part of the centripetal force, in

    order to keep the ball have enough centripetal force.So the (R) is dependant on the

    position of the ball. So the Contripetal force will not be larger than the required one.

    So the ball will always on track after passing through the highest point.

    Hope this can help you to solve your question/problem.

    :)

    資料來源: myself
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  • 天同
    Lv 7
    10 年前

    I don't think it would occur like that.

    After passing through the highest point, the speed of the ball would increase. It would press more hardly onto the rail. The normal reaction could then provide the necessary centripetal force.

    The event drawn on the diagram could only occur when ther is suddenly a drop in speed of the ball.

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