# Physics PAT Question (Q17,2012)

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#1
Having trouble with this question. It depicts a slider going down a slope from a height 'h' and then going up a parabola which reaches h then goes down. I would put B as the answer because at the start of the descent, the slider has a maximum gpe and then reaches a max kinetic energy at the bottom of the track ( right before the parabola starts), when it reaches the same height as it started at all its kinetic energy should be transferred to gpe right? So it would have no energy to keep it moving and so should just fall at that point.

The answer is A but I don't understand why! (It never reaches the top of the parabola). Maybe it has something to do with circular motion but I just can't find a worked solution!
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2 years ago
#2
(Original post by Biteri)
Having trouble with this question. It depicts a slider going down a slope from a height 'h' and then going up a parabola which reaches h then goes down. I would put B as the answer because at the start of the descent, the slider has a maximum gpe and then reaches a max kinetic energy at the bottom of the track ( right before the parabola starts), when it reaches the same height as it started at all its kinetic energy should be transferred to gpe right? So it would have no energy to keep it moving and so should just fall at that point.

The answer is A but I don't understand why! (It never reaches the top of the parabola). Maybe it has something to do with circular motion but I just can't find a worked solution!

For the slider to reach T, the slider needs to move at a certain speed at T. The speed depends on the radius of the circular track according to circular motion.

At T, the minimum speed is given by

weight of slider = mass × centripetal acceleration

Since the slider will be losing speed when it moves up the circular track, there will be a point when the speed is less than , it will lose contact with the track as it does not have enough speed to “undergo circular motion”. So it would not reach T.
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