Physics, 30.09.2019 07:30, amanda289

Emergency!

a 2 meter tall archer shoots an arrow with the speed of 20 m/s at a target positioned on the same horizon plane 30 m away. if the arrow is to hit the center of the vertical target, which is 2 meters above the ground at what angle to the horizontal should the arrow be launched. [given sin2a = 2sina. cosa]

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If I understand the question the arrow starts at 2m above ground and will try to hit a target 2m above ground 30m away. So if this is the case we can neglect the 2m altogether. It starts at some height (which we can call 0) and after its flight it lands at the same height. So we need to solve its vertical and horizontal position functions to find the angle. The vertical function will tell us how long it's in the air before it gets back to the height it started at. We then have to ensure the angle allows it to travel 30m horizontally in that time.
Vertical: a=-9.81m/s^2
v=-9.81t + 20sin(n). Where n is the angle
So vertical position is the integral of velocity
s=-9.81/2 t^2 +20t sin(n)
s=-4.905t^2+20t sin(n)=0
This can help us find n in terms of t. We need t such that the arrow traveling at 20m/s makes it exactly 30m. Using the formula s=vt
30=20t cos(n)
t=1.5/cos(n)
Putting this in our previous equation
-4.905(1.5/cos(n))^2+
20(1.5/cos(n))sin(n)=0
Now multiply both sides by (cos(n))^2 to get
-4.905(1.5)+20(1.5)cos(n)sin(n)=0
Or
-7.36+30sin(2n)=0
Now find n
7.36= 30sin(2n)
7.36/30=sin(2n)
2n=arcsin(7.36/30)
2n=14.2
n=7.1 degrees

answered: Guest

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answered: Guest

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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Emergency!

a 2 meter tall archer shoots an arrow with the speed of 20 m/s at a target p...