Recent content by crossfacer

1) In an experiment on Interference of sound, 2 loudspeakers are 0.8m apart and are driven in phase. The microphone is 1m from the loudspeakers. The frequency of the sound is set to be 500Hz. Explain why it is unsuitable to use sound of frequency, say 200Hz or 20kHz in this experiment. Is it...

I feel like my answer is not correct:frown:. I guess x should be about 0.5.

Homework Statement A unifrom disc A of radius 2m is cut as shown in the image. The cut out is also a disc of radius 1m. Find the distance of the two center of gravity before and after the paper disc is cut. http://crossfacer.com/circle.jpg Homework Equations...

I am a beginner in polarization, and questions keep raising when I revise this topic:frown: : Scattering: 1. After the molecule absorb the energy of incident light wave, the energy is reemitted in all direction. Why is it still a kind of polarization if the light emitted is in all...

Circular motion-----"slipping" problem Homework Statement The figure attached shows a man riding a motorcycle on the rough wall of a cylindrical room. He is performing uniform circular motion and does not slide down along the wall. If the man rides the motorcycle and performs circular...

Homework Statement There is a ship of mass M floating on a river. The upper portion of the ship has a uniform cross-sectional area A and the density of water is d. Now the ship is displaced a further depth y into the water and released. What is the resultant force acting on the ship when it is...

Actually there is a diagram next to the question. The diagram shows the Earth and two equipotential sufaces (only part of the surface is drawn, I can see two "curves" but I don't know whether it is circular or eliptical) P and Q is two points on the two equipotential surfaces respectively.

There is a question in the book: A space shuttle of mass 10000kg coasts in a spiral path towards the Earth from P to Q with its engine shut off. Take GMe=4.0*10^14 J/kg/m and radius of the Earth=6.4*10^6m and assum no frictional loss. Calculate the change in gravitational potential energy. The...

Thank you. The book also mentions that if the orbit is elliptical, the satellite can spiral towards the Earth even air friction is neglected. In fact why this happen? And why doesn't it happen if the orbit is circular? Thanks!

Thank you! In the past I thought that some potential of Earth will be canceled out by potential of the moon :-p

Homework Statement Given: G = 6.67*10^ -11 Nm^2kg^-2 Radius of Moon = Rm = 1.73*10^6 m Radius of Earth = Re = 6.37*10^6 m acceleration due to gravity = g = 9.8m/s Mass of moon = Mm Mass of Earth = Me Distance between the centre of the Earth and the centre of the moon = D = 3.8*10^8 m...

Homework Statement A well-known paradox is that the air friction due to the outer layer of the Earth's atmosphere will reduce the total energy of the satellite and therefore the satellite will move slower. But it is observed that the satellite actually moves faster. Try to explain this...

I haven't heard about it before. I will try to learn it by myself. Thank you:rolleyes:

Homework Statement The two plates of a parallel-plate capacitor initially carry equal amount of positive charge. If some charges are transferred from one plate to another, the charges on the plates are respectively +900uC and +100uC. The potential difference across the plates becomes 4V. What...

I am surprised to see so much replies! Thank you very much for your answer. I'll try to look it at a different wayo:)