Physics, 22.07.2019 19:30 dylalove4963

Astone is dropped from the upper observation deck (the space deck) of the cn tower, 450 m above the ground. a. find the distance of the stone above ground level at time t. b. how long does it take the stone to reach the ground? c. with what velocity does it strike the ground? d. if the stone is thrown downward with a speed of 5 m/s, how long does it take to reach the ground?

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Answer from: ahmetagayew2004

A) The stone moves along the vertical direction by unifom accelerated motion, with acceleration equal to g (gravitational acceleration), starting from initial position h above the ground and with initial velocity equal to zero. So, its vertical position follows the law:
$y(t) = h - \frac{1}{2}gt^2 = 450 - \frac{1}{2}(9.8)t^2 [m] = 450 - 4.9 t^2 [m]$

b) The time the stone takes to reach the ground is the time t at which its vertical position y(t) becomes zero:
0=y(t) =450-4.9 t^2

and if we solve it, we find
$t= \sqrt{ \frac{450}{4.9} }=9.6 s$

c) Since it is a uniform accelerated motion, the velocity of the stone at time t is given by
v(t) = v_0 -gt=-gt

where the initial velocity is zero: v_0 = 0

. The stone hits the ground at t=9.6 s, so its velocity at that time is
v(9.6s)=-gt=-(9.81 m/s)(9.6 s)=-94.2 m/s

where the negative sign means it is directed downward.

d) In this case, since the initial velocity is not zero, the position at time t is given by
$y(t) = h -v_0 t - \frac{1}{2}gt^2 = 450 - 5t -4.9t^2 [m]$
where v_0=5 m/s

is the initial velocity.
The time the stone takes to reach the ground is the time t such that y(t)=0, so we have:
450-5t-4.9t^2 =0

and by solving this equation, we find
t=9.1 s

Answer from: Quest

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.

Answer from: Quest

the correct choice is a .

do not post any more test or exam questions on

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Astone is dropped from the upper observation deck (the space deck) of the cn tower, 450 m above the...

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