An ion with a charge of+ is trapped in the earth's magnetic field. It suddenly picks up 2 electrons, and its charge becomes -1. How does its motion change? Assume the gain of the 2 electrons does not involve a mechanical force.
A. It reverses direction along the same spiral path.
B. It travels along the same spiral path at a greater speed.
C. It travels along the same spiral path at a lesser speed.
D. The rotation of its spiral path reverses direction.

D. The rotation of its spiral path reverses direction.

Explanation:

F = qvB (eq. 1)

where,

q = charge

v = velocity of the particle

B = strength of the magnetic field

 (eq. 2)

Where,

m = mass of the particle

r = radius of the orbit

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.

read more on -

see the picture for the vector

the magnitude of the vector by pythagorean theorem

r = √( (-10)^2 + (3)^2 ) = √109

magnitude = √109 units

the direction angle between vector and x-axis is

tan^(-1)(3/10) = 16.699

so the direction is approximately 16.7 degrees north of west