Reputation
273
Next privilege 500 Rep.
Access review queues
Badges
1 9
Impact
~16k people reached

  • 0 posts edited
  • 3 helpful flags
  • 196 votes cast
Apr
22
comment High Level Understanding Q: What *is* a magnetic/electric field?
I like this answer, but I have one question - what about energy? Is energy fundamental? Does an increase or decrease in the value of a field at a given location mean that there is now more or less energy at that location?
Apr
22
comment High Level Understanding Q: What *is* a magnetic/electric field?
"Like, for example: is the vector field a big soup of moving electrons," - Definitely not. If it was, your big soup of electrons would either need to be 1) a medium that was already there, that the EM wave is just passing through, or 2) emitted from the EM source, travelling along with the EM wave. We know it is not option (1) - google "aether" or "Michelson Morely experiment". We know it is not option (2), because the EM wave travels out from the source at the speed of light - electrons can't go that fast.
Mar
21
comment Calculate the height reached when 1/3 of original Kinetic Energy is lost
I think you are interpreting the question as "If the object is thrown upward with 1/3 less kinetic energy, what maximum height will it reach?", while the book means "If the object is thrown upward with the same original kinetic energy, at what height will the object have lost 1/3 of its kinetic energy?".
Feb
16
comment How do you tell whether a force acting on an inclined plane is going up or down in its perpendicular component to the plane?
By the way - you will do the same thing to gravity. You will make the original force of gravity the hypotenuse, and replace it with components parallel and perpendicular to the plane. This will show you how much gravity (the weight of the object) contributes to the normal force, and how much of the weight contributes to it accelerating down the plane.
Feb
16
comment How do you tell whether a force acting on an inclined plane is going up or down in its perpendicular component to the plane?
The advantage to the second technique is that the perpendicular forces have no effect on each other. So when calculating the normal force, you only have to look at the forces perpendicular to the plane, and can ignore the forces parallel to the plane. When calculating acceleration along the plane, you can ignore the perpendicular forces, and only look at the forces parallel to the plane.
Feb
16
comment How do you tell whether a force acting on an inclined plane is going up or down in its perpendicular component to the plane?
Physically, the meaning of the triangle is: You can remove the original force (the hypotenuse), replace it with the two perpendicular components, and the object won't know the difference - everything would behave exactly the same. So, when trying to calculate things like normal force and acceleration along the plane, you can either 1) just keep the original force as drawn, and use sine, cosine, etc. to try to calculate the normal force, etc., or 2) replace the original force with its parallel and perpendicular components, and then use them to reason about the normal force, etc.
Feb
16
answered How do you tell whether a force acting on an inclined plane is going up or down in its perpendicular component to the plane?
Feb
16
comment How do you tell whether a force acting on an inclined plane is going up or down in its perpendicular component to the plane?
What do you mean by that? Maybe you need to define "vertical" for us. Do you mean: perpendicular to the inclined plane, parallel to the inclined plane (i.e. "uphill"), or parallel to gravity?
Feb
16
comment How do you tell whether a force acting on an inclined plane is going up or down in its perpendicular component to the plane?
The 5N and 20N forces look like they are horizontal, and therefore would have no vertical component.
Jan
18
comment Expansion of the Universe
What do you mean by "bound by gravity"? Do you mean that, for example, a comet on a parabolic trajectory around our Sun will be affected by space expanding (since it is not bound to a closed orbit), but a comet on an elliptical trajectory will not? Or do you mean that if the gravitational force is of sufficient strength then you won't notice the effects due to space expanding?
Jan
13
comment Violation of the Newton's first law of motion in the movement of spacecrafts in the vacuum of space
You went wrong with: "The molecules of the gas are moving in any direction in the vacuum of space; they won't move in the space the same way that a metal ball will move." I'm not sure why you assume that the gas from a rocket sprays out in all directions. Maybe you are picturing the turbulence exhibited by rocket exhaust when the rocket is first leaving the launch pad?
Dec
7
comment How can angular velocity be constant even when there is a torque by friction?
"How can friction vanish?" - Friction disappears when there is no relative motion between the cylinder and the surface. So there is no torque being applied by friction. If the cylinder were to suddenly hit an ice patch, it would continue to roll exactly the same as it was before.
Nov
18
comment Explaining conservation of angular momentum with a disconnect
Nevermind - I was confused.
Nov
18
comment Explaining conservation of angular momentum with a disconnect
I think that the only revolving @Dylanthepiguy is asking about is around the probe. I don't think he's talking about the probe/instrument system revolving around a planet or anything like that.
Nov
18
comment Explaining conservation of angular momentum with a disconnect
I don't think this is correct. If I spin a baseball on a string, then let go of the string, the baseball does not continue to revolve around me - it travels in a straight line, tangent to the original orbit.
Nov
13
awarded  Citizen Patrol
Nov
5
comment Why is walking up stairs harder than walking normally?
To walk, you just have to lift one foot barely above the ground, tilt forward, and land on the foot. To climb a stair, you have to lift a foot to the next step, and then that leg has to lift your entire body up so that your other foot can be lifted.
Oct
26
suggested rejected edit on Why don't surfboards fly out the back of a utility truck when driving on the highway?
Sep
9
comment Source of energy for magnetic work?
"Well, I didn't do any work to separate the magnets." - Yes you did, when "I set two magnets on my desk such that...". Assuming the magnets were initially stuck together, you did work to pull them apart and place them on the desk with some separation between them.
Sep
9
comment Source of energy for magnetic work?
You have used up the magnetic potential energy due to the initial separation of the magnets.