Recent content by Cc518

Sorry, I just assumed that constructive interference means the interference is maximally constructive because I only know how to solve questions when the interference is maximally constructive or maximally destructive. I am not surprised that the answer is wrong because the textbook has lots of...

Homework Statement Two in-phase loudspeakers, which emit sound in all directions, are sitting side by side. One of them is moved sideways by 3.0 m, then forward by 4.0 m. Afterward, constructive interference is observed 1/4 and 3/4 of the distance between the speakers along the line that joins...

Thank you so much!

Because the object cannot move with the ball from point A to B, the momentum is not conserved?

Oh, I see :smile: Thank you for reply.

Homework Statement An object with a mass of 5kg is placed on a horizontal surface and it has a semi-circular orbit with radius 1m. Its left end is close to a baffle fixed on the ground. A ball with a mass of 1kg is released from the point A by static. The surface and the groove are both smooth...

The factor is less than 1? A0/At=√10^0.8 and At=e-t/τ A0 Then e-t/τ = 1/√10^0.8 t=1, I got τ=1.08s which is twice the answer, 0.54s, though, but I don’t see why I have to divide 1.08 by 2.

Amplitude will decrease by √8dB, right? Then why did you say ?

Thank you for reply:) So does that mean amplitude will decrease by a factor of √10^0.8 ? If so, then e^-t/τ =√10^0.8, t=1, I got τ=1.08s which is not the right answer:( Can anyone tell me where I went wrong? Thank you!

Homework Statement A vibrating standing wave on a string radiates a sound wave with intensity proportional to the square of the standing-wave amplitude. When a piano key is struck and held down, so that the string continues to vibrate, the sound level decreases by 8.0 dB in 1.0 s. What is the...

OK，thank you so much!

Sorry, I still don't understand how WA=0(work done on A equals zero) helps me to understand part b... If we only consider the interactions between A,B and C, excluding the external forces, the total change in kinetic energy is WB+WC=10-5=5J, which makes the total change in potential energy equal...

So if we consider A, B and C as one system, the ΔKtot is 14 + 13 =17J. Then the change in potential energy should be -17J since the energy is conserved in an isolated system, am I correct? But the answer says change in potential energy is 5J, I don't understand:sorry:

A is stationary which means its velocity doesn't change, therefore its change in kinetic energy is zero, therefore the work done on A is zero

The body has to move a distance d