VCE Physics Question Thread!

[09Ti08]

No, I think they were not fired from the same cannon. Why? Let's assume that they were, I don't think that the trajectories can be that much different, even though we were not given information about the distances between the ships.

I think the force exerted by a canon is quite large, but we don't know the distance of the two shells from the mouth of the cannon and their masses and sizes... These numbers do matter, as I need them for calculations. I can't really do anything if I assume too much...

So I think they were fired from two identical canon balls from the same position. That would make sense.

[lzxnl]

If they weren't fired from the same cannon, they may well be fired at different speeds.

In any case, we can't conclusively say that the two balls will hit each boat at the same time.

[09Ti08]

I totally agree. I was just trying to explore all the possibilities.
Anyway, the problem is getting unsolvable. However, because it's a question on a sac, we have to come up with an answer by making simplifications and/or assumptions.

[lzxnl]

Honestly, if I were in that situation, I'd just argue why there's no clear-cut answer.

[rhinwarr]

Can someone help with this question please? I'm not sure how to rearrange the circuit. The answer is supposed to be 83.3 ohms but from the circuit I drew I get 116.7 ohms.

[alchemy]

Can someone help with this question please? I'm not sure how to rearrange the circuit. The answer is supposed to be 83.3 ohms but from the circuit I drew I get 116.7 ohms.

I don't do Physics, so I hope this is correct. I think you found the effective resistance for the entire circuit, whereas the question asks to find it between P and R. Check the attached image for my drawing of the circuit, which is pretty much similar to yours. The path marked in red is the area the question concerns. The effective resistance of the first resistor (in parallel) is 1/[(1/100)+(1/100)]=50. The effective resistance of the other resistors from Q to R and the one below them is 1/[(1/100)+(1/100)+(1/100)]=100/3=33.3. Thus, the total effective resistance is 50+33.3=83.3.

[Yacoubb]

I have a few questions:

1. Describe the origin of the centripetal force that causes an object to follow a circular path.

2. I want to know whether I've approached this correctly.

Saturn has at least eighteen natural satellites, two of which are Titan and Tethys.

mass of Titan = 1.35 x 10^23 kg
radius of Titan = 2.6 x 10^6 m
period of Titan's orbit = 1.38 x 10^6 s
radius of Titan's orbit = 1.22 x 10^9 m
mass of Tethys = 7.4 x 10^20 kg
radius of Tethys orbit = 2.9 x 10^8 m

Calculate the gravitational field strength of the surface of titan.

g = GM/r^2.
G = 6.67 x 10^-11
M = 1.35 x 10^23 kg
r = 2.6 x 10^6 m

Is that value of r correct? Which radius do I use? How do I know which one to use in a case like this?

Help would be much appreciated. Thank you

[Bronzebottom64]

Is that value of r correct? Which radius do I use? How do I know which one to use in a case like this?

Help would be much appreciated. Thank you

Yes that is the correct value for the radius, the gravitational field strength is calculated purely on the object in question. Any gravitational field on the surface of a planet in the solar system (Earth) will also have external gravitational fields acting upon them as is the nature of matter in the known universe. The question is a bit ambiguous, however I believe what it's asking is what you have done. 

[EspoirTron]

I have a few questions:

1. Describe the origin of the centripetal force that causes an object to follow a circular path.

2. I want to know whether I've approached this correctly.

Saturn has at least eighteen natural satellites, two of which are Titan and Tethys.

mass of Titan = 1.35 x 10^23 kg
radius of Titan = 2.6 x 10^6 m
period of Titan's orbit = 1.38 x 10^6 s
radius of Titan's orbit = 1.22 x 10^9 m
mass of Tethys = 7.4 x 10^20 kg
radius of Tethys orbit = 2.9 x 10^8 m

Calculate the gravitational field strength of the surface of titan.

g = GM/r^2.
G = 6.67 x 10^-11
M = 1.35 x 10^23 kg
r = 2.6 x 10^6 m

Is that value of r correct? Which radius do I use? How do I know which one to use in a case like this?

Help would be much appreciated. Thank you

For the first part to your question: the centripetal force is always supplied by a real force. This could include the tension in a string or the frictional force between the tyres of a car and the road.
Let's first take the example of the tension in the string scenario. Say if I have a bucket of water attached to a string, as I begin to swing it in the circular path the tension will act towards the center of the circle, which is by consequence the centripetal force.
The second example is one that has popped up a few times on exams. So consider a 'normal' road; that is, one that hasn't been rained on or has much due so it's pretty dry. If a car wanted to go in a circular path around this dry road it would be quite possible. This is because there is a frictional force between the surface of the road and the car tyres which acts towards the center the circular path, and this too is the centripetal force. Often in calculations on horizontal surfaces you will denote this as the net force.
Caution: One of the reasons why you can't maintain such motion on an icy track is because there is little friction between the car tyres and the surface of the road. So as you speed up it becomes difficult to control the car and the car will leave the circular path at a tangent to the path.

[Yacoubb]

For the first part to your question: the centripetal force is always supplied by a real force. This could include the tension in a string or the frictional force between the tyres of a car and the road.
Let's first take the example of the tension in the string scenario. Say if I have a bucket of water attached to a string, as I begin to swing it in the circular path the tension will act towards the center of the circle, which is by consequence the centripetal force.
The second example is one that has popped up a few times on exams. So consider a 'normal' road; that is, one that hasn't been rained on or has much due so it's pretty dry. If a car wanted to go in a circular path around this dry road it would be quite possible. This is because there is a frictional force between the surface of the road and the car tyres which acts towards the center the circular path, and this too is the centripetal force. Often in calculations on horizontal surfaces you will denote this as the net force.
Caution: One of the reasons why you can't maintain such motion on an icy track is because there is little friction between the car tyres and the surface of the road. So as you speed up it becomes difficult to control the car and the car will leave the circular path at a tangent to the path.

Yes that is the correct value for the radius, the gravitational field strength is calculated purely on the object in question. Any gravitational field on the surface of a planet in the solar system (Earth) will also have external gravitational fields acting upon them as is the nature of matter in the known universe. The question is a bit ambiguous, however I believe what it's asking is what you have done. 

Thanks to you both!

[Rishi97]

Does anyone have any good ideas for EPI on electronics? I want to do somthing awesome/interesting

[Rod]

Does anyone have any good ideas for EPI on electronics? I want to do somthing awesome/interesting

Maybe you could investigate factors that affect a modulated signal. Like for example my friend was telling me that the radio in his car always gets distorted when a motorcycle is near his car, maybe because of the fact those 'drumming' noises are interfering with the modulated signal being formed by the carrier and input signal.

If we were to do another EPI I would base it on that, looks so fun.

Good luck Rishi

[Rishi97]

Maybe you could investigate factors that affect a modulated signal. Like for example my friend was telling me that the radio in his car always gets distorted when a motorcycle is near his car, maybe because of the fact those 'drumming' noises are interfering with the modulated signal being formed by the carrier and input signal.

If we were to do another EPI I would base it on that, looks so fun.

Good luck Rishi

Yeah that does sound fun Rod. But we haven't learnt anything about modulated signals at school. So would I still be able to do it?

[Rod]

Yeah that does sound fun Rod. But we haven't learnt anything about modulated signals at school. So would I still be able to do it?

Yeah you should be able to, it's unit 3 area of study 2 stuff, but confirm with your teacher just in case.

All my teacher when through was 'a low frequency input signal in increased by a carrier signal, and then we get our modulated signal.....'. And showed us one diagram. So yeah lol he didn't go through it with us a single bit but we still understand it.

It's just a suggestion, I would probably do it.

Best of luck!

[Rishi97]

Yeah you should be able to, it's unit 3 area of study 2 stuff, but confirm with your teacher just in case.

All my teacher when through was 'a low frequency input signal in increased by a carrier signal, and then we get our modulated signal.....'. And showed us one diagram. So yeah lol he didn't go through it with us a single bit but we still understand it.

It's just a suggestion, I would probably do it.

Best of luck!

I'll see some other options and ask my teacher as well. Thanks heaps Rod