Question

In the "Drop Zone" ride at Canada's Wonderland, riders are dropped from a great height and then decelerated safely to a stop before hitting the ground. One possible technological application of Faraday's principle and Lenz's law is the ride's braking mechanism. If the ride is simulated by dropping a magnet with the north side down into an open copper pipe,

a) What is the direction of current flow in the pipe?

b) What is the direction of the induced magnetic field?

c) Why does this situation result in decreased acceleration of the magnet/ride? Explain well.

d) Would this situation be any different if the south end of the magnet was dropped down instead? Explain.

The main question I am stuck on is part d - especially the explanation.

Answer 1

Introduction :According to lenzes law induced emf or current in a loop will always try to oppose change in magnetic flux linked with it. So it will try to oppose motion of magnet towards it or away from it.

According to flemings right hand rule if culred fingure represents current, thumb will indicate magnetic field.

1)When north pole is approaching copper ring with acceleration g an emf or current will induce in ring to make the side of ring facing magnets north pole becomes north to repel magnet or to oppose increase in magnetic flux linked with it. So current must be in anticlockwise direction to produce upward magnetic field lines(flemings rule) @as shown in in image(a).

2)induced magnetic field is upward as shown in image (a).That is because of anticlockwise current.

3)Repulsive force opposes the weight of magnet and hence resultant force on magnet will come down so it is decelerated. Mathematical steps are there in image (a). There I proved a<g.

4)If south end is dropped situation will be as shown in image (b)

There to oppose south side of magnet a clockwise current will induce i the ring to make upper face of ring to be south and it contributes magnetic field in downward direction . Here also acceleration decreases as in above case.