Multiple Choice (3 Viewers)

[Broodchuck]

To induce a current in a conductor, there must be a magnetic field perpendicular to the conductor. Its the basis of motors and generators, therefore if the wire is n/s or e/w one way will induce a current, the other orientation wont.

Not exactly, it doesn't have to be perpendicular, it just cant be parallel. Now, if I can strain my memory back to my physics days... the formula was F = BIlsin(theta(is that how its spelt?)), so changing the orientation will skrew the theta part

 

[noah]

no projectiles with angles of @ and 90-@ will have the same range.

 

[dipis]

no no

time will be the same for 40 degrees and 50 degrees cause they are similar but range will differ.

Imagine it ... throwing something at like 89 degrees will have hardly any range... so its B. shorter range

Nah, time differs for different angles because it goes higher in the sky and only gravity is what makes it fall. Go to this website:

http://galileo.phys.virginia.edu/classes/109N/more_stuff/Applets/ProjectileMotion/jarapplet.html

 

[cziLofty]

I disagree haboozin..after studying projectile motion in 3 different courses if you throw a particle at 40 and 50 it will land in exactly the same spot as they are complimentry. however the 50 degree particle will stay in the air for longer so the answer was C.

Also i thught it was funny...my physics teacher always said with MC the first answer is neva A. I look at it for a while and thought, screw that lol.

 

[cziLofty]

lol sorry haboozin but you got owned

 

[dangerousdave]

i thought that was fucking hard multiple choice.
These are the ones i guessed:
Q4 C
Q6 B
Q12 B
Q13 C
Q15 D

 

[Broodchuck]

1. C is wrong because you are thinking about vertical velocity being 0 however at the top there is still horisontal velocity
if you did 3unit maths this would be a very easy concept to understand.
and ofcourse the velocity is always changing so its A.R

I admit it, I am sorry, I don't do three unit maths.

8. battaries only work on DC current... have you ever seen a AC battary? It doesn't even make sense.
anyways u picked D which is again definatly wrong (because the graph u are thinking of is VOLTAGE VS TIME not CURRENT VS TIME)

Yes, your right, batteries work on DC current but why are you talking about that? If your commenting about my answer for question 15 then there is never a mention of AC or DC.

Now, voltage and current are always proportional to each other, so if your correct, then the right answer would be the exact inverse of that graph. now, there are no other graphs that like the inverse of that graph... so i must conclude that you are wrong.

9. it could be B but definatly not A... Q will NEVER fall before R

Think about it...

 

[dragon fan]

Question 5 is definately (B)

I'll give you an example.

I will use an anology of the degrees of loft on a golf club.

A driver has very low loft but goes the furthest
A wedge has a high loft but doesnt go very far

THerefore that automatically rules answer for A

Projectile Motion experiments will prove that the height will have no effect on the time of the flight.

 

[dipis]

I also think Q8 is C because even though batteries are DC when the switch turns on there will be a quick change in the magnetic field which will affect the galvanometer and then the current will subside after when the current is flowing and thhere is no more magnetic field

Also another reason it could be C is bc even if u disregard the whether the battery is AC/DC then the battery will still go flat which will make the current less

 

[cziLofty]

dragon fan goto http://galileo.phys.virginia.edu/cl.../jarapplet.html which dippy said too and press fire...then change angle to 20...then come back and hit ur golf ball

 

[dangerousdave]

Question 5 is definately (B)

I'll give you an example.

I will use an anology of the degrees of loft on a golf club.

A driver has very low loft but goes the furthest
A wedge has a high loft but doesnt go very far

THerefore that automatically rules answer for A

Projectile Motion experiments will prove that the height will have no effect on the time of the flight.

I got C for question 5. I even did some calculations to make sure.
pretending u = 1
when its 40 degressm time of flight is 0.131
when 50 degrees, time is 0.156

horizontal, cos40 * 0.131 = 0.1
cos50 * 0.156 = 0.1 :. same range

 

[dipis]

Question 5 is definately (B)

I'll give you an example.

I will use an anology of the degrees of loft on a golf club.

A driver has very low loft but goes the furthest
A wedge has a high loft but doesnt go very far

THerefore that automatically rules answer for A

Projectile Motion experiments will prove that the height will have no effect on the time of the flight.

Yes a drive does go far but thats because its got lots of speed to get it far. The max range for any projectile will always be achieved if you fire it at an angle of 45.

Also you cant compare those two actions because ur using two different clubs and its a totally different technique when you hit the ball. Not that i play golf or anything but its pretty obvious

But height does affect the time, if you shoot something at the same velocity it will always be up for longer if it goes higher

 

[Dumsum]

1. A
2. D
3. B
4. C (this question was strange, but I thought maybe it would fall back to Earth)
5. C
6. B (wtf was with this question)
7. A (I had trouble with the right hand rule, but the idea was to mentally rotate the thing 90 degrees in your mind)
8. C
9. B
10. B
11. B
12. A
13. A
14. B
15. D (had no idea, put D because there was only one other D in the thing lol)


fruck this exam was hard

 

[Mellybum]

Question 5 is definately (B)

I'll give you an example.

I will use an anology of the degrees of loft on a golf club.

A driver has very low loft but goes the furthest
A wedge has a high loft but doesnt go very far

THerefore that automatically rules answer for A

Projectile Motion experiments will prove that the height will have no effect on the time of the flight.

Maybe my brain's just been fried from all the HSC stress, but I'm finding it hard to accept your ideas bout the max height not affecting time of flight. Ur trying to tell us that if i throw two balls, both at the same velocity, angle etc, one with max height of 10m, the other with max height of 100m they will have the exact same time of flight despite the difference is distance travelled??? Right... I dont understand...

 

[thunderdax]

1. A
2. D
3. B
4. D (wierd question, but if you reduce the velocity then it would go into a smaller elliptical orbit which is why i picked it)
5. C (range is the same for x and 90-x, and when fired at 50 it would have a larger vertical velocity)
6. B
7. A (use right hand palm rule and Lenz's Law)
8. C (Although it is a DC supply, once it starts there is a momentary change in flux as the current increases. It then goes back down to zero)
9. C (No eddy currents in R since there isn't a complete circle)
10. C (Although you guys seem to think B and I had no clue)
11. B
12. A
13. C (since extra electron in the valence band. If it was A, the conduction band would be slightly lower)
14. B
15. D

 

[Dumsum]

OK everyone, for that orbit question (Q4) here is my thinking: Yes, slower speed means larger orbit. But maybe it's not that so much, as larger orbit meaning slower speed. See, for the object to move outwards like that, it would have to GAIN Gravitational Potential Energy. Where would this come from? It said the rocket was fired forward halving speed, so if anything, energy has been lost. I think C (falling back to earth) is the best answer.

 

[mrboredman]

answer to question 5 : napoleans cannonball

http://galileo.phys.virginia.edu/classes/109N/more_stuff/Applets/ProjectileMotion/jarapplet.html

check this out

sucked in C

 

[dragon fan]

Ah well question 5 is c.
Still looking for over 85 %

 

[dipis]

OK everyone, for that orbit question (Q4) here is my thinking: Yes, slower speed means larger orbit. But maybe it's not that so much, as larger orbit meaning slower speed. See, for the object to move outwards like that, it would have to GAIN Gravitational Potential Energy. Where would this come from? It said the rocket was fired forward halving speed, so if anything, energy has been lost. I think C (falling back to earth) is the best answer.

It says the rocket is fired forward that reduces its orbital speed, it says nothing about the speed it needs to get there just that it was fired in order to reduce obital speed. Therefore it must be A. Because geo-stationary satellites travel much slower than low earth orbitters

 

[thunderdax]

Think about Newton's concept of escape velocity. When the cannon is fired slower, it curves into the earth. So when this rocket goes slower, what do you think its going to do?