VCE Physics Question Thread!

[KiNSKi01]

Cheers man! Never seen that equation before 

Didn't know how to derive an equation from equations on formula sheet which would actually help 

[minhalgill]

why cant we use momentum to show whether the collision was inelastic or elastic? why do we have to use KE?

[minhalgill]

how many significant figuires should we use in phyics?

[KiNSKi01]

why cant we use momentum to show whether the collision was inelastic or elastic? why do we have to use KE?

Yo!
Whether a collision is inelastic or elastic depends on whether energy is conserved. Using momentum will not show whether a collision was inelastic or elastic. Although within a system momentum may be conserved (basically always in the case of VCE questions), this doesn't necessarily mean energy is conserved  (in most questions the collision will be inelastic) as energy is dissipated/loss by thermal, sound etc.

Hope that helped!

[sweetiepi]

how many significant figuires should we use in phyics?

Typically the number of significant figures that is used in the question.
Pretty sure there was a discussion on this recently.

[minhalgill]

Yo!
Whether a collision is inelastic or elastic depends on whether energy is conserved. Using momentum will not show whether a collision was inelastic or elastic. Although within a system momentum may be conserved (basically always in the case of VCE questions), this doesn't necessarily mean energy is conserved  (in most questions the collision will be inelastic) as energy is dissipated/loss by thermal, sound etc.

Hope that helped!

this helped alot, but im just confused about how the momentum can be conserved yet energy is not?

are clipping voltages in the study design?
mod edit: merged posts.

[Bri MT]

this helped alot, but im just confused about how the momentum can be conserved yet energy is not?

Momentum is m*v whereas kinetic energy is .5*m*v^2
If you double the mass and halve the speed you'll get 2m*.5v = mv (momentum is conserved)  and .5*2m*(.5v)^2 = .25*m*v^2 (kinetic energy is not conserved)

An example of this as a question is: you have a trolley being pushed along the ground with mass m and speed v. An object of mass m is dropped into the trolley from directly above it. Find the new speed of the trolley if momentum is conserved (2 marks). Is the collision elastic? (3 marks)

[minhalgill]

are inverting amplifiers in the study design?

[KiNSKi01]

are inverting amplifiers in the study design?

not exactly sure what you are referring to 

https://www.vcaa.vic.edu.au/Documents/vce/physics/PhysicsSD-2016.pdf

Have a read of this and it might answer a few of your questions 

[minhalgill]

can someone please help with this question? i get why the emf graph is constant, i just dont get why its negative?

[Bri MT]

can someone please help with this question? i get why the emf graph is constant, i just dont get why its negative?

Lenz's law  / the fact that there's a negative in the emf equation (-N * (delta phi)/(delta t)

[minhalgill]

why have they drawn a ray of light reflected inwards for (b)?
do we always draw this reflected ray of light as well as the refracted one?

[S200]

If you've ever tried this experiment with an actual light box, you would see that some-times a ray will refract out of the material as well as reflect back into it...

It's something to do with being less than the critical angle...
#HighlyTechnicalAnswer

[KiNSKi01]

Helloooo

Mostly I know how to answer Lenz's Law questions BUT i am confused by q12c on the 2017 NTH exam (photo of question is attached)

I understand the change in flux and that the the magnetic field produced by the current must oppose this change but I am confused about the direction the current flows. When using the RH grip rule must the field inside or outside the coil oppose the change in flux or am I just totally off the mark with this question!??

Help is much appreciated 

[Yertle the Turtle]

Helloooo

Mostly I know how to answer Lenz's Law questions BUT i am confused by q12c on the 2017 NTH exam (photo of question is attached)

I understand the change in flux and that the the magnetic field produced by the current must oppose this change but I am confused about the direction the current flows. When using the RH grip rule must the field inside or outside the coil oppose the change in flux or am I just totally off the mark with this question!??

Help is much appreciated 

The change in flux relates to the change in flux within the loop. Therefore you would use the right hand grip rule to show you that the induced emf will produce a current that will cause a magnetic field coming out of the page in 23a. Therefore the current will travel from X to Y.