2I1pt] gure. Answer the i ener the unifm TS magnetic fie data peed of 33 ms and

Question

2I1pt] gure. Answer the i ener the unifm TS magnetic fie data peed of 33 ms and with an angle ofor with respect to the field lines, as shown in the >x Angle A) The particle's speed varies as it passes through the B-Field B) The initial force on the particle is in the +y direction. C) The path of the particle is a closed circle since the force is normal to the velocity D) The y-component of the particle's velocity is unchanged as it passes through the B-Field. E) The work done by the field on the particle is zero since the force is normal to the displacement. Answer:

Explanation / Answer

[Underscore is used here to denote a vector quantity.]

From the outset, what you need to recall is the Lorentz force law:

F_ = q(E_ + v_ x B_)

Since E_ = 0 here, that's just
F_ = qv_ x B_

and this is true whatever the angle between v_ and B_. In any cross product,
the result is both vectors, so
F_ v_, i.e., F_•v_ = 0,
and so no work is done by the field on the particle.

A) False

because of no work done = no change in kinetic energy = no change in speed

B) False

initially, because v_ is in the xy-plane, with a +y-component, so v_ x B_ has only a (+y) x (+x) = (-z)-component

C) False (path will be helical)

D) False

E) True
And because
F_ B_
and B_ || x, the force is x, and so the x-acceleration is 0.

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