VCE Physics Question Thread!

[BlinkieBill]

Hey
I am doing a projectile distance practical for the epi. We're shooting nerf gun bullets at different angles and heights above the ground.
I was wondering what a good research question/aim would be for it. My teacher said something about terminal velocity and comparing practical results to theoretical (using formulas) results, but I'm not too sure about the research question still.

Any help is appreciated. Thanks

[Guideme]

Please help me with these two questions Thank you a lot!
In general more heat is lost through the roof of a house then through the walls. Explain why this is so?

Often weather reports for skiing resorts will use the term 'wind chill factor'/ Explain the meaning of this term using appropriate thermodynamics principles and mechanisms

[TooLazy]

I just want to confirm, when an object is decelerating the net force is in the direction opposite to its movement?

[Alwin]

Please help me with these two questions Thank you a lot!
In general more heat is lost through the roof of a house then through the walls. Explain why this is so?

Often weather reports for skiing resorts will use the term 'wind chill factor'/ Explain the meaning of this term using appropriate thermodynamics principles and mechanisms

If you think about how heat would travel (does it rise or does it fall) I think you'll be able to see why more heat is lost at the roof.
In terms of the wind chill factor, it comes down to the idea that you have air flowing over your skin rather than being stationary around you. A loose analogy would be letting your coffee cool down by letting it rest, or stirring your coffee (making it cool faster). Hopefully you should be able to take it from here

I just want to confirm, when an object is decelerating the net force is in the direction opposite to its movement?

 Yup! That would be correct

[Mattjbr2]

http://i.imgur.com/XtCj6OP.png
Is the book's answer correct? Doesn't the flux increase when you increase the number of turns of wire? I'm getting conflicting information from multiple places: https://physics.stackexchange.com/questions/219881/is-the-number-of-turns-in-a-loop-part-of-the-magnetic-flux the dude says N (number of turns of wire) affects ϕ. Also: http://i.imgur.com/hzwGz0n.png the book even plainly states that. However, nowhere in the book is N included in the ϕ=BA equation.
What's going on!?

[Mattjbr2]

Bump. Sac in 3 hours 

[sweetiepi]

http://i.imgur.com/XtCj6OP.png
Is the book's answer correct? Doesn't the flux increase when you increase the number of turns of wire? I'm getting conflicting information from multiple places: https://physics.stackexchange.com/questions/219881/is-the-number-of-turns-in-a-loop-part-of-the-magnetic-flux the dude says N (number of turns of wire) affects ϕ. Also: http://i.imgur.com/hzwGz0n.png the book even plainly states that. However, nowhere in the book is N included in the ϕ=BA equation.
What's going on!?

Hey, sorry for my late reply,
I'd definitely go with the with equation ϕ=nBA because the number of coils does increase the flux generated.
As there is the new study design, books are churned out very rapidly and generally contain a few mistakes.

[Syndicate]

Hey, sorry for my late reply,
I'd definitely go with the with equation ϕ=nBA because the number of coils does increase the flux generated.
As there is the new study design, books are churned out very rapidly and generally contain a few mistakes.

The number of coils doesn't exactly effect the magnetic flux as the area remains the same (from a VCE point of a view, you might be correct from a first year perspective, but I am not really sure of that) . Magnetic flux is defined as the amount of magnetic fields going through a certain area, so the amount of coils doesn't affect it.
(This is directly out of my book as well, so I am not really sure if I am correct either  )

[zsteve]

From the way it's put in VCE, to the best of my understanding:
- Flux is related to the total 'amount' of field passing through a given surface area (so )
- The presence of multiple coils does affect the current/potential produced, but this is accounted for when dealing with Faraday's Law

[Mattjbr2]

Therefore is my book's answer correct or incorrect?

[Syndicate]

Therefore is my book's answer correct or incorrect?

Your book is right with the equation part, but, for question 2 (faraday's experiment question), I believe he used a coil with many turns as it increases the strength of static magnetic field around the coil, which thereby results in a greater EMF induced. They didn't have modern technology to measure the induced EMF, so if only a small EMF was induced, then they wouldn't really be able to calculate it (or know if something really happened or not).

[Mattjbr2]

Your book is right with the equation part, but, for question 2 (faraday's experiment question), I believe he used a coil with many turns as it increases the strength of static magnetic field around the coil, which thereby results in a greater EMF induced. They didn't have modern technology to measure the induced EMF, so if only a small EMF was induced, then they wouldn't really be able to calculate it (or know if something really happened or not).

What about question 3? The back of the book gives 3.0x10^-5 Wb but the worked solutions give 3.0x10^-3 Wb and neither took into consideration the 50 turns.

[Syndicate]

What about question 3? The back of the book gives 3.0x10^-5 Wb but the worked solutions give 3.0x10^-3 Wb and neither took into consideration the 50 turns.

It is most likely a misprint. The solutions with 3.0 x 10^-3 Wb is the correct one.

[gamma032]

Hi everyone!

I've been trying to calculate the uncertainty in a couple of calculations, but I'll just present the hardest.

I'm finding the gravitational potential energy (m*g*h) of an object, and I measured:

• The measurement uncertainty in the mass to be ±0.005kg
• The uncertainty in the height to be ±0.0005m

I'm using g=9.8.

What would the final uncertainty of the GPE calculations be?

[zsteve]

Hi everyone!

I've been trying to calculate the uncertainty in a couple of calculations, but I'll just present the hardest.

I'm finding the gravitational potential energy (m*g*h) of an object, and I measured:

• The measurement uncertainty in the mass to be ±0.005kg
• The uncertainty in the height to be ±0.0005m

I'm using g=9.8.

What would the final uncertainty of the GPE calculations be?

From memory, what one must do when adding two quantities is to deal with fractional error. Consider c=a+b. Then the fractional error in c is given by:



Where a, b, c are the mean values of a, b, c; and the Delta values are the error margins.

This is also how we deal with errors for division