Which dog has the most kinetic energy?

a. a dog of mass 14 kg running with speed 2 m/s
b. a dog of mass 14 kg running with speed 3 m/s
c. a dog of mass 11 kg running with speed 5 m/s
d. a dog of mass 12 kg running with speed 4 m/s

Nobody actually needs to know how much kinetic energy any of these dogs has.  

The purpose of this question is to help you discover whether you know how to calculate kinetic energy, and then to give you some practice at doing it.

You have to calculate the kinetic energy of each dog, and then review your results to see which dog has the most.

The whole secret behind working this problem is the formula for the kinetic energy of any object:

Kinetic Energy = (1/2) · (mass) · (speed)²

The little ² next to 'speed' means 'squared' or 'multiplied by itself'.

(speed)² means (speed · speed) .

So, in order to calculate how much kinetic energy an object has, here's what you do:

-- Take the object's speed.  Multiply the speed by itself.

-- Take that number and multiply it by the object's mass.

-- Take that number and throw away half of it.

So now here we go:

Dog A:  KE = (1/2) (14 kg) (2 m/s)² = 28 Joules

Dog B:  KE = (1/2) (14 kg) (3 m/s)² = 63 Joules

Dog C:  KE = (1/2) (11 kg) (5 m/s)² = 137.5 Joules

Dog D:  KE = (1/2) 12 kg) (4 m/s)² = 96 Joules

==> Dog C has more kinetic energy than any of the other 3 dogs.

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.