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seen Jun 14 at 5:47

May
24
comment Electric Flux through metal plate by uniformly charged wire
find the electric field at a point on plate, then find the normal component, then integrate. post your calculations if didn't find the answer.
May
24
comment Electric Flux through metal plate by uniformly charged wire
you also need the distance
May
24
comment Optical path difference
because we assume that our lens is perpendicular to the reflected rays (i.e. parallel to DF). so the blue line should be parallel to DF.
May
24
comment what is the temperature (and pressure) of the oxygen inside an oxygen bottle?
It is stored both as high pressure gas and liquid. It does not equilibrate because it's being cooled. en.wikipedia.org/wiki/Oxygen_therapy#Storage_and_sources
May
22
comment Black Body Golf Balls
You could use a cube of the same volume. It has more surface area and none of its rays will be re-absorbed.
May
20
comment Applying unsteady Bernoulli (to a balloon attached to a tube)
@timni A massive pendulum feels a large torque but it also has a large inertia and they cancel out. A capacitor with more charge also has more current while discharging. Here you have more mass but also more pressure.
May
20
comment Applying unsteady Bernoulli (to a balloon attached to a tube)
@timni Change of volume should be equal to volume flow rate. I think it's pretty much intuitive. The assumption that pressure at the surface of balloon and mouth of the tube is equal is valid when we could neglect effects of the velocity in the balloon. Apart from that it's make sense.
May
20
answered Applying unsteady Bernoulli (to a balloon attached to a tube)
May
19
reviewed Reviewed Do we weigh more when standing near massive buildings?
May
19
comment Bernoulli Equation for isentropic ideal gas flow
@mcocdawc it's not equivalent. to be isentropic it must be frictionless (since friction is irreversible) but it's not sufficient. frictionless flow with heat transfer (rayleigh flow) is also non-isentropic.
May
19
reviewed Reviewed Bernoulli Equation for isentropic ideal gas flow
May
19
reviewed Reviewed Do holes have physical existence?
May
19
revised Do wind turbines convert the kinetic energy of air?
added 157 characters in body
May
18
comment Solve unsteady state Bernoulli equation for flow in a pipe
you should probably upload a sketch showing where is the cut, and geometry of the pipe. just to be clear by "the closed off pipe" you mean fluid can not flow out except through the cut?
May
18
comment How is the kinetic energy of the wind transferred onto a lift based wind turbine?
I posted a new answer to that question, which answer your question as well: physics.stackexchange.com/a/184730/23679
May
18
answered Do wind turbines convert the kinetic energy of air?
May
18
comment Which point in the graph does a parachute open?
Apart from this, the graph also look suspicious. Parachute is fully open about the first point that you have greatest negative slope which should be a little after B. Immediately after B the slope should be somewhat gentler. And before D there's a small speed increase which is not real. The reason that the slope decreases between A and B is probably the drag of human body itself.
May
18
comment Which point in the graph does a parachute open?
I don't think the test maker had this mind but usually free fall parachutes have 2 canopies. Main canopy is large and will experience a huge force if opened at high speed that could rip it apart, damage the parachute and injure the parachutist (because of sudden great force). First they deploy a smaller canopy and when they've slowed down to near terminal velocity they deploy the main canopy to reduce the terminal velocity.
May
18
comment If induced voltage (back-emf) is equal and opposite to applied voltage, what drives the current?
the analogy between current and force is not correct. force is direct cause of acceleration which changes velocity, current is more like velocity than acceleration.
May
17
reviewed Reviewed Potential and Electric field