Physics: Post your doubts here!

[Choi WW]

I'm not sure, but I think that a point source will cause two completely in phase waves with same speed to be produced (because of diffraction), but perhaps the two loudspeakers will produce waves that are slightly out of phase with each other. My imagination is not good enough to imagine what effects this may have, but perhaps this may help you arrive at your explanation. Maybe somehow two waves with a phase difference are not able to cause complete destruction.

Oh, maybe that one can also be a factor. Thanks a lot.

 

[Abdul Hanan]

http://theallpapers.com/papers/CIE/AS_and_ALevel/Physics (9702)/9702_s12_qp_22.pdf
Q1/b) please ...

 

[princess Anu]

I asked my teacher, he said that it may be due to background sound. since they haven't mentioned about a sound proof room.

Oh, maybe that one can also be a factor. Thanks a lot.

 

[omg]

http://theallpapers.com/papers/CIE/AS_and_ALevel/Physics (9702)/9702_w13_qp_22.pdf
Q. 2)a) please thnx.

we have to find the distance. the formula for distance is d= v*t. we know the speed of a radio wave is 3*10 ^8
now we need the time. time base setting is 0.2 * 10 ^-6 and the distance between the emitted and reflected pulse is 4 blocks so multiply them and you will get the time. put it in the formula and you will get the distance

 

[omg]

http://theallpapers.com/papers/CIE/AS_and_ALevel/Physics (9702)/9702_s12_qp_22.pdf
Q1/b) please ...

Did you do it by the formula absolute/true value * 100. and did you multiply r by 4?

 

[Abdul Hanan]

we have to find the distance. the formula for distance is d= v*t. we know the speed of the a radio wave which is 3*10 ^8
now we need the time. time base setting is 0.2 * 10 ^-6 and the distance between the emitted and reflected pulse is 4 blocks so multiply them and you will get the time. put it in the formula and you will get the distance

Oh so we count the blocks from each pulse's middle. Got it. One thing you forgot to mention was to divide in the end by 2 as the wave reflects and then comes back..
thanks

 

[omg]

Oh so we count the blocks from each pulse's middle. Got it. One thing you forgot to mention was to divide in the end by 2 as the wave reflects and then comes back..
thanks

Yes , you will divide it by 2 to get the distance from source to reflector. missed that out X_X

 

[Sahil Gupta]

Explain this to me. I got the density 2.685. and % uncertainty of mass and volume as 1.7 and 5% respectively. I don't know how to get final uncertainty of density as 0.18 in the marking scheme. Shouldn't we just add 1.7 and 5?

 

[omg]

Explain this to me. I got the density 2.685. and % uncertainty of mass and volume as 1.7 and 5% respectively. I don't know how to get final uncertainty of density as 0.18 in the marking scheme. Shouldn't we just add 1.7 and 5?

did you convert grams into kg and cm into m while finding density? i am getting it as 2685.2 after conversion

 

[omg]

Explain this to me. I got the density 2.685. and % uncertainty of mass and volume as 1.7 and 5% respectively. I don't know how to get final uncertainty of density as 0.18 in the marking scheme. Shouldn't we just add 1.7 and 5?

did you multiply the uncertainity of volume by 3?

 

[Sahil Gupta]

did you multiply the uncertainity of volume by 3?

yes i did all that and i got the uncertainty of mass and volume. but i can't figure out how to get the uncertainty of density with those values. here is ms

 

[omg]

yes i did all that and i got the uncertainty of mass and volume. but i can't figure out how to get the uncertainty of density with those values. here is ms

percentage unc. = absolute/ true value. we have true value and percentage unc. ( 5 + 1.7)for density. put the values in the formula. you will get 0.18

 

[Abdul Hanan]

help please thanks

 

[Sahil Gupta]

percentage unc. = absolute/ true value. we have true value and percentage unc. ( 5 + 1.7)for density. put the values in the formula. you will get 0.18

what? which one is absolute value and which one is true value? should i take perc. uncertainty as 6.7?

 

[omg]

View attachment 53543
help please thanks

find percentage uncertainity of all the values by the formula absolute/true value * 100. add them. multiply the uncertainity of r by 4. and you should get the answer. and the absolute value is the one in points like 0.001 and the true value is 1.20 waleys.

 

[omg]

what? which one is absolute value and which one is true value? should i take perc. uncertainty as 6.7?

true value is the value of density which is 2.685 and absolute is 6.7%.
(6.7/100 * 2.685) willl give you the answer

 

[Sahil Gupta]

true value is the value of density which is 2.685 and absolute is 6.7%.
(6.7/100 * 2.685) willl give you the answer

Thanks a ton

 

[Abdul Hanan]

find percentage uncertainity of all the values by the formula absolute/true value * 100. add them. multiply the uncertainity of r by 4. and you should get the answer. and the absolute value is the one in points like 0.001 and the true value is 1.20 waleys.

i tried. i still can't lead to the final answer... can you give a brief working please? thanks.

 

[omg]

i tried. i still can't lead to the final answer... can you give a brief working please? thanks.

sure but how do we attach the files here? .-.

 

[Abdul Hanan]

sure but how do we attach the files here? .-.

Drag it from your PC folder to the writing box here. or from phone just click "upload a file" button beside the "post reply button and find the file...