VCE Physics Question Thread!

[skrt skrt]

(GMm/r^2)=(mv^2/r), this is the equation used to find Kepler's laws for natural or artificial satellites,
I was just wondering why the two equate each other, sorry for the late reply

[lzxnl]

(GMm/r^2)=(mv^2/r), this is the equation used to find Kepler's laws for natural or artificial satellites,
I was just wondering why the two equate each other, sorry for the late reply

One side is the magnitude of the gravitational force, which is directed inwards. The other side is the centripetal force requirement for circular motion. As we're assuming circular orbits, the condition for moving in such an orbit is Fnet = mv^2/r, and this force must be directed inwards. The gravitational force must then meet this condition in direction and magnitude. Otherwise you don't move in that orbit at that speed or orbital radius.

[skrt skrt]

Thanks

[Seno72]

Hey guys, what's the purpose of slip rings in an alternator. And also, for every half turn, do the slip rings reverse their polarity?

[sweetiepi]

Hey guys, what's the purpose of slip rings in an alternator. And also, for every half turn, do the slip rings reverse their polarity?

The purpose of slip rings is to maintain a continuous connection between the wire and armature, in comparison to a split-ring commutator, which does not.

Slip rings do in fact reverse the direction of the current halfway.

[Seno72]

The purpose of slip rings is to maintain a continuous connection between the wire and armature, in comparison to a split-ring commutator, which does not.

Slip rings do in fact reverse the direction of the current halfway.

Thanks

[Seno72]

Hi guys. When you are ordering STAV exams for 2018, do they only give you just one exam paper or many of them for just one pack (e.g physics) ? Because it costs quite a lot.

[KiNSKi01]

Hey guys,

I'm not sure if this is the right place to ask. I'm thinking of picking up Physics Unit 2 without Unit 1. Is this manageable?

In year 10, my school taught general science which included topics of motion and electricity. Is there anything new taught in Unit 1 Physics that I would need to catch up on? Any tips?

Thanks! 

Eh, you would have to do some catching up if your school is going to do exams on the whole 1/2 course content; however, in saying that considering you already have knowledge in motion and electricity (two topics relevant to 3/4) what you've missed out in unit one isn't that important. So i would say if you want to do physics and you think you can do well definitely pick it up now rather than later

[Guideme]

Can anyone help me with 39 a and b thank you in advance

[IonianDeo]

How would you go about approaching this question?

[Bri MT]

How would you go about approaching this question?

Ignore the piece of vertical wire and just use the right hand rule for the solenoid

[IonianDeo]

Why is it that at the end of parallel oppositely charged plates that the electric field lines begin to bulge outwards? What causes the bulging?

[Floatzel98]

Why is it that at the end of parallel oppositely charged plates that the electric field lines begin to bulge outwards? What causes the bulging?

Think about all the individual point charges that make up the plates. In the center of the plates, far away from the edges, the electric field looks uniform. If we think of the electric field of a two point charges together, they cancel (or deflect) in the direction connecting them (see image). If you put heaps of these next to each other, the next result is an electric field perpendicular to the line of charges (perpendicular to the plate). So in the center of the plate, we see a uniform electric field. Now consider the very last charge, at the very edge of the plate. There is no charge adjacent to this one and so there is only cancellation of the electric field on one side. The resultant electric field is a sum of a vector perpendicular to the plate and one 'diagonally' away (i.e the electric field of a point charge). Combined with the same effect on the oppositely charge plate, this gives the bulge effect in the electric field at the edges of the plate.

Hopefully that helps

[IonianDeo]

In gravitational, electric and magnetic fields, what is meant by a uniform field and a static field? What are the differences?

[sweetiepi]

In gravitational, electric and magnetic fields, what is meant by a uniform field and a static field? What are the differences?

Not sure about static fields but here's what I remember about uniform fields:
A uniform gravitational field means that there is no gravitational effect at all when in free fall.
A uniform magnetic field is when magnetic induction has the same magnitude and the same direction at all the points in the region.
A uniform electric field is when there are two straight parallel electrodes or plates that have a potential difference between them.