A proton with a velocity in the positive x-direction enters a region where there is a uniform magnetic field B in the positive y-direction. You want to balance the magnetic force with an electric force so that the proton will continue along a straight line. The electric field should be in the:

- positive x-direction

- positive z-direction

- negative y-direction

- negative x-direction

- negative z-direction

- negative z-direction

Explanation:

First of all, we have to determine the direction of the magnetic force acting on the proton.

The direction of the magnetic force acting on a moving charge can be determined by using the right hand rule. For a positively charged particle:

- Index finger: direction of the motion of the particle

- Middle finger: direction of the magnetic field

- Thumb: direction of the force

For a negatively charged particle, the direction of the thumb must be reversed.

In this problem, we have a proton (positive charge), and we have:

- Direction of motion: positive x

- Direction of the field: positive y

Therefore, by using the right-hand rule, we see that the thumb points towards z-positive direction: so, this is the direction of the magnetic force.

Therefore, the proton is deviated towards z-positive direction due to the magnetic force; in order to balance this and make the proton continuing along a straight line, the electric force must be in the z-negative direction.

The electric force experienced by a charged particle has the same direction of the electric field (if the charge is positive) or opposite direction (if the charge is negative): in this problem, the proton is positive, so the direction of the electric field must be the same of the force, therefore

-  negative z-direction

elly's long hair:

a. if the salon only takes cash, then this isn't the problem. it doesn't matter how much she has in her checking account.   she can't get a haircut until she has the cash.

b. if she has overdraft protection, then there's no problem.   she can go ahead and write a check that her account can't cover, then sometime later, pay the bank some outrageous usury for loaning her a few bucks for a few days, but with beautiful hair.

c. if elly has some principles, and doesn't want to write a bad check, then now she has a problem.   her desire for the new hairstyle is in conflict with her honesty and integrity.

d.   if the bank will not process a check she writes, then even if she had a million $$ in her account, she couldn't use any of it.   the amount she has in her account is not the problem.   and if i may suggest, she might as well close her checking account, and put the money where it'll work for her.   it's not doing her a bit of good in a checking account, since she can't write any checks.

justin can't pay the full balance:

a. he can't even handle the credit limit he has now.   under no circumstances should he ask for a higher limit.

b.   he can ask for the grace period to be extended.   but that's no solution, the bank will almost certainly refuse anyway, and there are much better options.   he knew the rules of his credit card when he started using it.

c.   he definitely should pay the interest on the balance, plus as much of the balance as he can cover at the same time.

d.   he definitely should pay the minimum otherwise they could shut down his card.   he should also pay as much more as he possibly can.   he should also remember the awkward situation he's in, stop buying stuff on credit that he can't afford, and avoid adding any more debt.

i'd say that justin's best best option isn't on this list of choices.   what he has to do:   pay as much as he can at least the minimum payment plus as much more as he can and then avoid adding more debt.

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