Physics: Post your doubts here!

[qwertypoiu]

Inelastic collision: a piece of plasticine of mass 0.20 kg falls to the ground and hits the ground with a velocity of 8.0 ms-1 vertically downward. It does not bounce but sticks to the ground.
1- Calculate the momentum of the plasticine just before it hits the ground.
2-State the transfers of momentum and of kinetic energy of the plasticine which occur as a result of the collision.
...WHATS THE ANS OF PART 2 ..........HELP PLZ.....WID FULL EXPLANATION!!!!

1. Momentum = 0.2kg * 8 ms^-1 = 1.6 kgms^-1
2. Momentum is never gained or lost. Such illusions may be created in a case like this, where a ball with momentum suddenly loses it all. However, as the ball gains momentum as it comes closer to the earth (because it accelerates) the earth is also gaining momentum in the opposite direction towards the ball. We don't notice this because this is a very small amount due to massive size of earth (my book said half diameter of an atom or something).
Similarly, energy is neither created nor destroyed. However, kinetic energy is not always conserved, since it may be converted to other forms. In inelastic collisions like this, kinetic energy was converted to heat energy.

 

[qwertypoiu]

elastic collision: a neutron of mass 1.00 u traveling with velocity 6.50 x 105 ms-1 collides head on with a stationary carbon atom of mass 12.00 u. The carbon atom moves off in the same direction with velocity 1.00 x 105 ms-1. Calculate the velocity of the neutron after the collision. State what happens to the kinetic energy as a result of this collision.??????????????????

Let v be velocity of neutron. Total momentum before = total momentum after
1u * 6.5*10^5 + 12u * 0 = 1u * v + 12u * 1.00*10^5
Let's just divide by u on all terms:
6.5*10^5 = v + 1.2*10^6
v = -5.5*10^5
Negative just means the neutron is moving in opposite direction.

Now since it says it's an elastic collision, we know that the kinetic energy must have been conserved. We can verify that:
Total kinetic energy before = 0.5*1u*(6.5*10^5)^2 = 2.11u*10^11 Joules
Total kinetic energy after = 0.5*1u*(-5.5*10^5)^2 + 0.5*12u*(1.00*10^5)^2 = 2.11u*10^11 joules

 

[ashcull14]

Let v be velocity of neutron. Total momentum before = total momentum after
1u * 6.5*10^5 + 12u * 0 = 1u * v + 12u * 1.00*10^5
Let's just divide by u on all terms:
6.5*10^5 = v + 1.2*10^6
v = -5.5*10^5
Negative just means the neutron is moving in opposite direction.

Now since it says it's an elastic collision, we know that the kinetic energy must have been conserved. We can verify that:
Total kinetic energy before = 0.5*1u*(6.5*10^5)^2 = 2.11u*10^11 Joules
Total kinetic energy after = 0.5*1u*(-5.5*10^5)^2 + 0.5*12u*(1.00*10^5)^2 = 2.11u*10^11 joules

Hillarious! thnk uuuuuu

 

[Sinzzzz]

see solution 527 at
http://physics-ref.blogspot.com/2015/04/physics-9702-doubts-help-page-102.html

thanks alooooot

 

[Choi WW]

The answer is D so I thought it's because there is the difference in the path travelled by the waves, so there is difference in intensities, amplitudes of the waves, so there would be no complete destructive interference. But then, for the young's double slit experiment, there should be also no complete destructive interference according to what I thought, but they consider it as complete destructive interference, right?

So, I was searching for it, then, I saw the explanation on the webstite, http://physics-ref.blogspot.com/2015/03/physics-9702-doubts-help-page-93.html.

They said it's because the speaker isn't point source.... what does it mean by that and how the factor 'point source' affect the result.....

Also, is my thought in the beginning wrong?
Past Exam Paper – November 2014 Paper 11 Q26

 

[eliyeap]

View attachment 53476 The answer is D so I thought it's because there is the difference in the path travelled by the waves, so there is difference in intensities, amplitudes of the waves, so there would be no complete destructive interference. But then, for the young's double slit experiment, there should be also no complete destructive interference according to what I thought, but they consider it as complete destructive interference, right?

So, I was searching for it, then, I saw the explanation on the webstite, http://physics-ref.blogspot.com/2015/03/physics-9702-doubts-help-page-93.html.

They said it's because the speaker isn't point source.... what does it mean by that and how the factor 'point source' affect the result.....

Also, is my thought in the beginning wrong?
Past Exam Paper – November 2014 Paper 11 Q26

Im not sure about the point sources but the way i look at is that the middle of XY will have the highest intensity(highest peak) because its a zero order. Then as you go further from the middle, lets say to the first order the intensity gradually decreases. The 2 speakers are coherent sources, meaning they have the same amplitude and phase difference. Its the path difference between them that forms then interference pattern on the screen XY

 

[Choi WW]

Im not sure about the point sources but the way i look at is that the middle of XY will have the highest intensity(highest peak) because its a zero order. Then as you go further from the middle, lets say to the first order the intensity gradually decreases. The 2 speakers are coherent sources, meaning they have the same amplitude and phase difference. Its the path difference between them that forms then interference pattern on the screen XY

But the answer is D, can you please explain me the reason why they don't have complete destructive interference (not zero intensity)?

 

[eliyeap]

But the answer is D, can you please explain me the reason why they don't have complete destructive interference (not zero intensity)?

https://www.google.com/search?q=you...nx.org%2Fcontent%2Fm42508%2Flatest%2F;875;521
The interference pattern on the screen should like this in terms of intensity. The peaks are where constructive interference occurs while the troughs between each peak is where destructive interference occurs. For path difference, when constructive interference occurs, the path diff must be n(lambda) where n can be 1,2,3 and so on. n is basically the no of order. When n=0, which would be in the middle you would have the maximum intensity of a bright fringe. As the n increases, the intensity of the bright fringes decreases. Dark fringes have no intensity as it is already dark, you can't make it darker.

 

[Choi WW]

https://www.google.com/search?q=young's double slit experiment&rlz=1C1KMZB_enMY614MY614&tbm=isch&tbo=u&source=univ&sa=X&ei=xKVQVd-KF6SwmAWLoYDoDg&ved=0CDAQsAQ&biw=1241&bih=584#imgrc=mdwZhBYE58VwmM%3A;hZqAo6hjXQTxXM;http%3A%2F%2Fcnx.org%2Fresources%2Fdc45f72de39c65b1e7f2cf1a0ec14598%2FFigure_28_03_06a.jpg;http%3A%2F%2Fcnx.org%2Fcontent%2Fm42508%2Flatest%2F;875;521
The interference pattern on the screen should like this in terms of intensity. The peaks are where constructive interference occurs while the troughs between each peak is where destructive interference occurs. For path difference, when constructive interference occurs, the path diff must be n(lambda) where n can be 1,2,3 and so on. n is basically the no of order. When n=0, which would be in the middle you would have the maximum intensity of a bright fringe. As the n increases, the intensity of the bright fringes decreases. Dark fringes have no intensity as it is already dark, you can't make it darker.

However, for the question, D, which is answer has no position having zero intensity right?

 

[princess Anu]

is the direction of tension correct? the one marked with black pen

 

[qwertypoiu]

View attachment 53476 The answer is D so I thought it's because there is the difference in the path travelled by the waves, so there is difference in intensities, amplitudes of the waves, so there would be no complete destructive interference. But then, for the young's double slit experiment, there should be also no complete destructive interference according to what I thought, but they consider it as complete destructive interference, right?

So, I was searching for it, then, I saw the explanation on the webstite, http://physics-ref.blogspot.com/2015/03/physics-9702-doubts-help-page-93.html.

They said it's because the speaker isn't point source.... what does it mean by that and how the factor 'point source' affect the result.....

Also, is my thought in the beginning wrong?
Past Exam Paper – November 2014 Paper 11 Q26

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.

 

[buckle_crackk]

The Young modulus of the metal of a wire is 0.17 TPa. The cross-sectional area of the wire is 0.18 mm2

what does the letter "T" in TPa here stand for?

 

[princess Anu]

The Young modulus of the metal of a wire is 0.17 TPa. The cross-sectional area of the wire is 0.18 mm2

what does the letter "T" in TPa here stand for?

tera, 10^12

 

[buckle_crackk]

tera, 10^12

thank you

 

[afrolina]

wh

what is the assumption supposed to be in part two?View attachment 53450

which year?

 

[eliyeap]

However, for the question, D, which is answer has no position having zero intensity right?

Ok, i finally get what your asking about. Sorry about that. I think there's no 0 intensity because the speakers are connected to an ac power supply. In an ac circuit, the current changes direction. http://www.answers.com/Q/Is_a_speaker_usually_driven_with_AC_or_DC_current

 

[amal sharkawi]

can anyone answer this question plz ????????

 

[farhan141]

Is it B?

 

[princess Anu]

its not Cie

wh

which year?

s

 

[princess Anu]

can somebody help with this
its Q4 2010j/23