Firefighters need to go from their resting quarters on the second floor to their equipment, 10 feet below, in a hurry.
(a) how fast would an 85 kg firefighter be moving at the bottom if he just jumped from the second floor to the first?
(b) what would be his kinetic energy when he got there?
(c) now using a pole to slide down, the firefighter arrives at the bottom with a velocity of 1.5 m/s. how much work is done by the friction of the firefighter holding the pole?
(d) how great is the force of friction, based on your answer to c.

a)  t = 0.622 s , v = 7.73 m / s , b)  K = 2539 J , c)  -2443.4 J , d)    fr = 803.75 N

Explanation:

A) when the fireman from the second floor is in a free fall motion the time to arrive, we can calculate it with kinematics

       y = v t + ½ g t²

When you jump your initial speed is zero

      y = ½ g t²

      t = √2y / g

Let's reduce the magnitude to the SI system

    y = 10 feet (0.3048 / 1 foot) = 3,048 m

    t = √ (2 3,048 /9.8)

    t = 0.622 s

The speed at this point is

   v² = v₀² + 2 g y = 0 + 2g y

   v = √ (2 9.8 3.048)

   v = 7.73 m / s

B) The kinetic energy is

    K = ½ m v²

    K = ½ 85 7.73²

    K = 2539 J

C) The relationship between work and kinetic energy is

   W = ΔK = - K₀

The initial kinetic energy is zero because when its high speed is zero.

    = ½ m v²

   = ½ 85 1.5²

    = 95.6 J

  W2 = 95.6 - 0 = 95.6 J

The variation of work in free fall less with friction

    ΔW = W2 -W

    Δw = 95.6 -2539

   ΔW = -2443.4 J

This is the work done by the friction forces

C)

   W2 = fr d cos θ

The angle is 180º because the friction opposes the movement

   W2 = - fr d = -2443.4

   fr = 2443.4 / d = 2443.4 / 3,048

   fr = 803.75 N

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.

c

explanation: