Homework Help: physics

Posted by Jon on Sunday, April 6, 2008 at 1:05pm.

1)For incomplete cancellation to occur, opposite pulses must have.

A)equal amplitudes
B)different energies
C)equal pulses
D)equal displacements

I think there is a typo on A because my book reads: if the opposite pulses have unequal amplitudes, cancellation is incomplete. So I think A should read unequal amplitudes. It also talks about displacement but I choose A if there is a typo.

2)For the medium to remain undisturbed as two pulses pass the same point, they must have.

A)equal amplitudes
B)opposite amplitudes
C)different amplitudes
D)both A and B

I got C

physics - Jon, Sunday, April 6, 2008 at 2:27pm
Was my other post deleted for any particular reason? Here it is again

1)Doubling the amplitude of a wave will double the amount of energy the wave can transfer.

true

2)What happens when a wave reaches the boundary of a new media?

it would reflect back
physics - bobpursley, Sunday, April 6, 2008 at 2:50pm
I agree on the first, on the second I disagree. For the medium to be undisturbed, the two waves have to completely cancel.
On the third, no. How is energy related to amplitude?
On the fourth, the answer is complicated. If the new media has a wave resistance exactly the same as the intial medium, the wave moves on thru. If not, then some of the energy is reflected back, some is transmitted. If the new medium has zero or infinite resistance, then all of it will be reflected back.
physics - Jon, Sunday, April 6, 2008 at 3:06pm
On the third, waves with greater amplitudes transfer more energy
physics - Jon, Sunday, April 6, 2008 at 3:11pm
For the 2nd, is it A? What's the difference between B and C
physics - Jon, Sunday, April 6, 2008 at 3:44pm
On the 4th:

A)reflect back
B)continue moving
C)either A or B
D)it would stop

Since you gave that explaination, would it be C?
physics - bobpursley, Sunday, April 6, 2008 at 4:27pm
C on the fourth.

Now on second, opposite amplitudes add to zero.

On the third, Energy is proportional to the square of amplitude.
physics - Jon, Sunday, April 6, 2008 at 4:58pm
Ok, I think I understand the 3rd. It doesnt double, it quadruples, so it's false

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