A student is conducting experiments with gliders on a horizontal, frictionless track. In trial 1 of an experiment, a glider moves with speed V, and collides elastically with another glider that is initially at
rest. In trial 2, the setup is identical except that the gliders stick together during the collision. How
does the speed of the two-glider system's center of mass change, if at all, during the collision in
each trial?
Trial 1
Trial 2
Does not change
Does not change
A B
Does not change
Decreases
C
Decreases
Does not change
D
Decreases
Decreases

acceleration = (change in speed) / (time for the change)

change in speed = (20-120)= -100 m/s.

1.5 min = 90 sec

acceleration = -100/90 = -1.11 m/s^2.

we don't care about the 150kg or the 2,500 meters. they don't make any difference.

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the answer is the first electromagnet (a). this is because it has more coils around the ferromagnetic material. increasing the number of coils increases the surface area in which the metal interacts with the current in the coil. this enables more atoms in the metal to become aligned hence becoming more magnetized.