Aamc 11, ps #31

[riseNshine]

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Hi everyone,

I was wondering if you could help me with #31. I don't understand why the work done by air resistance is negative or how you calculate work by air resistance and just assume its magnitude is less than that of gravity. thanks.

For #19, why doesn't answer choice C work? They have 3 different masses also.

#35, I just don't understand the explanation they provide at all.

#49, why isn't D a right answer?

thanks in advance!!! really appreciate the help

 

[tendiw]

If you posted the question and answer stems here, i could give you a detailed solution

 

[tendiw]

Question 19
You are trying to study the effects of mass so the selected masses must be different. Now another thing is you experiment must be controlled so every mass must be release at the same point, that is why A is correct

Question 31
In the first 600m the person is in free fall, that mean the work done by gravity is greater than that done by air resistance on the person because the person is "accelerating in the direction of gravity", because the person is not at terminal velocity, the force from air resistance and gravity are not equal, the person is falling down so gravity has the greater force over the 600m and thus its magnitude is great. As for the work done by air resistance, it doesnt have to be negative, it could be positive AS LONG AS gravity's work is opposite to it. If air resistance was positive the gravity most be negative as they work against each othert but gravity as a greater magnitude.

Question 35
Use PV=nRT. This equation tells you if temperature drops, so will pressure

Question 49
I think you made a calculation error, the force due to water is 100,000N and then the force due to the tank is 9,500N. If you add them up you get 109,500N. Watch your calculations.

 

[riseNshine]

Thank you so much tendiw!! sorry, could u explain why for question 50, d cannot be the right answer (i accidentally wrote#49 instead of 50).

thanks again!

 

[tendiw]

Post question 50 here.

 

[temptasian]

riseNshine, I don't know if you're still waiting for an answer to #50. It's a matter of reading the graph carefully.

Answer choice D says that at a pH of 8 and V of -0.1, Fe(OH)2 is the predominant form of iron, which is not true. At that point, Fe(OH)3 is the predominant form of iron.
Best way to answer this question is to use process of elimination to knock out answer choices.

 

[JLeBling]

I ****ing figured it out!!! And it isn't complicated at all.

Work by gravity = (Force of gravity)(distance)

Work by air resistance = (Force of air resistance)(distance)

SINCE the dude doesn't hit terminal velocity until 600m, meaning Fg > Fa until 600m, but since both forces are applied for an equal distance (that is 600m), then obviously B is the correct answer.

|Wa = (Fa)(d)| < |Wg = (Fg)(d)|

Godamnit, it's so stupid that it's smart.