VCE Physics Question Thread!

[Syndicate]

Hi
few more astronomy questions!

What is the nature of cosmic microwave background radiation?
A)faint uniform x-ray glow
B)bright uniform x-ray glow
C)faint uniform radio signal
D)weak and patchy glow at visible wavelengths

The major cause of a supernova is:
A)gravitational collapse of the core of a massive star
B)exhaustion of nuclear fuel

Any help would be really appreciated as I have a test tomorrow! 

Question 1: C
Question 2: A

[TheAspiringDoc]

Question 1: C
Question 2: A

reasoning?
And for the first Q, it's not really uniform is it?!

[sweetiepi]

How would I be able to solve this?

[JellyBeanz]

How would I be able to solve this?

Fc = Fnet = W − N
 As N = 0:
 Fc = W = mg
 Fc = 1200 × 10
 Fc = 12000

Fc=mv^2/r

v^2= Fc*r/m

v= √12000*10/1200

[sweetiepi]

Fc = Fnet = W − N
 As N = 0:
 Fc = W = mg
 Fc = 1200 × 10
 Fc = 12000

Fc=mv^2/r

v^2= Fc*r/m

v= √12000*10/1200

Thanks so much!

[strawberry7898]

Can someone explain to me what modulation is and how it is done?

[Maz]

hey...can someone please help me with this?
Find the mass of an electron for the alpha decay (4.003u) of Po-214 (213.995u) to Pb-210 (209.984u). is this consistent with the alpha particle having an energy of 7.68 MeV....
the answer is 7.46 MeV

Thankyou so much in advance

[Peanut Butter]

Can someone please help me with this question?

A car enters a roundabout at 24 kmh-1 travelling in an easterly direction and leaves the roundabout at 18 kmh-1 travelling in a southerly direction. Calculate the change in velocity of the car (include the direction).

Thanks

[Adequace]

Can someone please help me with this question?

A car enters a roundabout at 24 kmh-1 travelling in an easterly direction and leaves the roundabout at 18 kmh-1 travelling in a southerly direction. Calculate the change in velocity of the car (include the direction).

Thanks

I'd assume you could use change in v = v(f) - v(i), afterwards using vector addition which would require pythag.

Edit: I got 30m/s with direction pointing southwest.

[alanyin1]

Hi, I have a question about DIODES that may not be covered in VCE Physics.

If I have 2 diodes arranged in series, both having a switch-on voltage of 0.7V but my supply voltage is strictly within the range of (0.7, 1.4) Volts (exclusive), what happens?

I remember my teacher from last year saying that electrons are already present in the wire and that they do not "begin flowing" from the negative terminal of the battery to the positive terminal. If this is the case, the closest one to the battery isn't necessarily the answer. He also explained P-N junctions in semi-conductors to us at one stage, which may be involved in the answer.

I asked my teacher last year during a Prac Period and he replied simply with a "you should try and find out" but I never actually got around to seeing what happens. I have a couple of speculations as to what happens:

1. Either Diode 1 or Diode 2 turn on, but the other remains off. The battery supplies its total voltage, but since not enough is supplied to turn both on, one takes 0.7 and the other takes the remaining and thus does not reach the required switch-on voltage. Perhaps each time this happens, it is a random process as to which one turns on?

2. Neither turn on, but this is probably the least logical answer. Imagine a Diode and Ohmic Resistor arranged in series; the Diode will always use 0.7 V, regardless of how the series circuit is arranged, given that the supply voltage >0.7V. Therefore, shouldn't speculation 1. be more feasible?

3. When I attended the ATARNotes Physics Headstart Lecture at RMIT during the holidays, I asked Alwin the presenter this question. He explained that both would be on, but would be dim. Both would receive a voltage in-between 0 and the switch-on voltage of 0.7. Since in reality, the "boundary" between "on" and "off" is not as clear-cut as 0.7V, there is a "zone" where they are "on." Therefore, both are on but are dim.

However, if the 3rd option is true, if I were to supply 0.6 V to a circuit containing only 1 diode, shouldn't it be "on"? Shouldn't each coulomb of charge expend 0.6 Joules of energy to cross the P-N junction?

I tried to find an answer to this question on Google, but the circumstance might have been too specific to type into Google and couldn't find a suitable solution

[Swagadaktal]

Can someone please help me with this question?

A car enters a roundabout at 24 kmh-1 travelling in an easterly direction and leaves the roundabout at 18 kmh-1 travelling in a southerly direction. Calculate the change in velocity of the car (include the direction).

Thanks

Correct me if I'm wrong, but isn't this a question of pythag?
So you get 24 km/h east and 18 km/h south, soo 24^2 +  18^2 and then sq root that answer
You should get 30 km/h
So the change in velocity is 30 km/h south east   --- IS THIS CORRECT?

[alanyin1]

Regarding the velocity question above^ wouldn't the direction be [arctan(18/24)+90 degrees from North] ASSUMING that the same amount of time was used to travel in the respective velocities? Or do we just assume that the journey would be exactly SE due to the roundabout entrance/exits? If the same amount of time is used to travel at the velocities, it wouldn't be an isosceles triangle would it?

If we were to further scrutinise the question (probably not necessary), because we are travelling in a circle, wouldn't there be horizontal and vertical components to the respective velocities?

[Swagadaktal]

Regarding the velocity question above^ wouldn't the direction be [arctan(18/24)+90 degrees from North] ASSUMING that the same amount of time was used to travel in the respective velocities? Or do we just assume that the journey would be exactly SE due to the roundabout entrance/exits? If the same amount of time is used to travel at the velocities, it wouldn't be an isosceles triangle would it?

If we were to further scrutinise the question (probably not necessary), because we are travelling in a circle, wouldn't there be horizontal and vertical components to the respective velocities?

erm can you get that spesh outta here
Nah jks - I don't personally think VCE Physics goes into that much detail - I may be wrong but I find it highly unlikely that they have questions of that kind of depth.
Can someone concur?

[alanyin1]

Haha, yeah I agree I see things under too much of a spesh perspective, probably not needed for this question or Physics 3/4 (in general) I imagine.

[JellyBeanz]

Could someone pleeeease help me on the following question?

A car and driver of total mass 850 kg are travelling east along a straight road at a constant speed of 75.0 km/h. The car collides with a rubbish bin of mass 120 kg, which had been left on the road. The bin becomes wedged under the car within 0.350 s. The driver removed his foot from the accelerator and did not apply the brakes during collision.

1) Calculate initial momentum of the car
2) what is the final momentum of car-bin system
3) determine the speed of the car immediately after collision.
4)What is the change in momentum of the rubbish bin during the collision?
5) determine the magnitude of the average force exerted on the bin by the car.
6) What is the direction of the average force exerted by the bin on the car?

I've done the questions, but i don't have the solutions and i want to know if i am correct, could someone please help me with explanations for each answer.

sorry for the long question.