VCE Physics Question Thread!

[PB]

yep, that formula only works when there is no friction.

[PB]

Oh and Rishi, for your split/slip ring question. The full definitions can be found in my cheat sheet under the section Electric Power. And neither is "better" per se, rather they both have different functions.
SLIP rings are used to "collect" the AC current generated from generators while SPLIT rings facilitate the constant rotation of motors.
You should try to understand how these rings achieve those feats though, and not just memorise the answers

[Yacoubb]

how would you do these questions

What is the acceleration of the train 10 s after starting?



What is the acceleration of the train 40 s after starting?

With velocity-time graphs, acceleration can be calculated from the gradient.

So:

(a) 20m/s / 10s = 2m/s/s

(b) 40m/s / 40s = 1m/s/s

We can validate this because we can see that the graph eventually plateus; an indication of the fact that the object is travelling at constant speed (at which gradient = 0).

[Rishi97]

Oh and Rishi, for your split/slip ring question. The full definitions can be found in my cheat sheet under the section Electric Power. And neither is "better" per se, rather they both have different functions.
SLIP rings are used to "collect" the AC current generated from generators while SPLIT rings facilitate the constant rotation of motors.
You should try to understand how these rings achieve those feats though, and not just memorise the answers

Thanks PB
Yeah I'll check your cheat sheet on this info. 

[knightrider]

thanks guys the answers say ~1.3 m s-2 ,  ~0.5 m s-2

[knightrider]

how would you draw an acceleration–time graph for the bus

[Stew_822]

With velocity-time graphs, acceleration can be calculated from the gradient.

So:

(a) 20m/s / 10s = 2m/s/s

(b) 40m/s / 40s = 1m/s/s

We can validate this because we can see that the graph eventually plateus; an indication of the fact that the object is travelling at constant speed (at which gradient = 0).

Hello there,
The acceleration you've calculated in (a) is the average acceleration for the first 10 seconds. The question is asking the accerelation at ten seconds after starting, meaning that you need to draw a line at a tangent to the gradient at that point and calculate the gradient from that line, as the acceleration isn't linear since the graph isn't linear. You can see that there is a lot of initial acceleration, but it dies off later. So although the average acceleration for the first 10s is 2m/s/s, the acceleration at say 2s is greater than this and the acceleration at say 8s is less than this (and obviously then the acceleration at 10s is less).

I hope this makes sense and helps. When I calculated the gradient, I didn't bother drawing a line - I basically guestimated. I can draw you guys a pic if you like.
Cheers,
Stewart

[Stew_822]

how would you draw an acceleration–time graph for the bus

Have you read the chapter?

You find the accelation of each linear portion of the graph (you can find it using rise over run as this v-t graph is linear) and graph the acceleration against time.

[knightrider]

Have you read the chapter?

You find the accelation of each linear portion of the graph (you can find it using rise over run as this v-t graph is linear) and graph the acceleration against time.

Yea thanks but how would you find the acceleration for 6 seconds or 8 seconds for the bus

[Stew_822]

You can see the acceleration is the same for 6s or 8s as the gradient is the same. So you do rise over run for that section of the graph and that is your acceleration for that section of the graph. Try googling "finding gradient of a graph" if you are having trouble doing this, there would be plenty of tutorials out there.

[knightrider]

How would you do the following questions

[knightrider]

Q1 Hint: What does the gradient of a velocity-time graph tell you?

Spoiler

Acceleration

Q2,3,4 Hint: What does the area under a velocity-time graph tell you?

Spoiler

Displacement

If you still need help just post again

Thanks for tips but i still need help

[knightrider]

how would you do the following questions

[Stew_822]

Hello knightrider,

When asking questions and for help, it is better if you let us know what you are struggling with specifically, rather than just saying you need help. For example, you could tell us how you attempted the problem and that way we would know where a mistake may have been made and point you in the right direction.

I remember that question with the bus and Anna from last year, I had to ask my teacher.

You can usually find the worked solutions by googling "heinemann physics 11 worked solutions chapter X" where X is obviously the chaper you're up to.

I hope this helps.

Cheers,
Stewart

[hyunah]

can someone please help me?
An electron moving north enters a magnetic field
that is directed vertically upwards.
If the electron’s motion was inclined upwards
at an angle, as well as travelling north, what
would be the path of the electron?