Year 12s: what will be the first way you research your future options? >>

Official OCR A2 G484 June 2016 [Module 1] [90UMS]

Scroll to see replies

Reply 360

AlistairMcDonald

Original post by rm761

lol same, seems impossible tho

Our galaxy weighs ~1x10^43, so that would be a VERY heavy star :P

Reply 361

Danny_L

Original post by Zonothene

As its a binary system you have to use this if you wish to do it using kepler's 3rd law (i.e adding the two masses together in the equation).

So I'm ****ed.
Great. Goodbye 100% ums. ****ing ********

Reply 362

President J

Original post by victoria98

Screwed up the KE graph..., thought the maximum was 80mJ. Such a silly error... It was two marks though, what would the other mark be for? Also will there be ecf for maximum speed with 80mJ, or will they only give ecf for the time period?

So the max was 50mj right?

Reply 363

AlexeiLipov

Original post by Pyslocke

**** sake. I had KEmax as 80mj. So that means my second part of the answer is wrong too. How many marks would I lose for that?

I can't remember how many marks the graph sketching was, I think 1 mark. So you only lost 1 mark because the other parts of the question you will get error carried forward.

Reply 364

President J

Original post by rm761

lol same, seems impossible tho

It's a star. The sun is 1x10^30. Binary stars are usually massive.

Reply 365

adsy9

Original post by Asiimov

I think most are saying 5/4pi, I think you might have miscounted :frown:

i got 5/8PI as the phase difference, would 5/4PI mean its out of phase by 1/4PI???

Reply 366

Pyslocke

Okay, so for the question about Mars' moons. What did everyone write for the speed of the moon? It said EXPECT to see so I said you would expect it to decrease in speed because the mean gravitational field acting on the moon decreases? Assuming their masses affect each other. But seriously... wtf

Reply 367

jamesgates1

For S2 mass could i do this:

F = GM1M2/r1^2 = M1v1^2/r1 which M1 cancels
GM2/r1^2 = v1^2/r1
Rearrange for M2.

I'm not sure what answer i got but is that a correct method?

Reply 368

jazzypeas

DIFFICULTY POLL:
http://www.thestudentroom.co.uk/showthread.php?t=4176590

votevotevote :smile:

Reply 369

mjcejnc32

Original post by President J

It's a star. The sun is 1x10^30. Binary stars are usually massive.

thats why i didnt think the 41 was too weird, i thought s2 must be so big that s1 revolves around it like the earth does around the sun fgs, then i googled mass of largest star ffs

same

I got 10^33 as the mass of star 2. Is this right?

Reply 372

Zonothene

Original post by Smeagul

I got 10^33 as the mass of star 2. Is this right?

that is the correct power yes

Reply 373

ridazdi

There goes my A

Go to hell G484.

Reply 374

neyjunior

for the fireman question, i did 92g - 8.3gsin55 :/ is this correct?

Reply 375

President J

Original post by neyjunior

for the fireman question, i did 92g - 8.3gsin55 :/ is this correct?

Had to be plus. Hose would push you back.

Reply 376

Zonothene

Original post by neyjunior

for the fireman question, i did 92g - 8.3gsin55 :/ is this correct?

No, the vertical component of the contact force is equal to the weight of the fireman plus the vertical component of the impulse of the water. Answer = 92g + 8.25*(whatever the speed of the water was)*sin(55)