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comment How far up an object is its gravitational potential energy taken from?
It is also only true if the body can be considered rigid and in the same orientation before and after, or symmetric enough that you don't care. Otherwise, you split up the body into lots of small bits, compute the change in height of each bit, and add them up.
Aug
26
answered Estimation of the age of Earth
Aug
26
comment Electromagnetic radiation from AC circuit?
And every circuit where conditions are changing is AC. A simple digital gate radiates when the inputs change in such a way that the output changes. It may (very likely) be within the allowable limit, but it does radiate. +1
Aug
26
answered How is Liouville's theorem compatible with the Second Law?
Aug
24
answered How to turn the light stronger than your strength in start
Aug
24
answered How does differing surface resistance in a parallel plate capacitor effect the field strength?
Aug
24
answered How is the value of Standard gravitational parameter for Earth derived?
Aug
23
reviewed Approve How much energy is released from the splitting of a single hydrogen atom?
Aug
23
answered How much energy is released from the splitting of a single hydrogen atom?
Aug
23
answered Which 'error' to choose random or absolute?
Aug
15
answered Are there an even number of particles in the universe
Aug
13
comment What should the brake force in this problem be?
No, I was saying there is another term, the braking force. Just add it in. Imagine you hook a spring to the particle and pull it enough that the spring applies 260N. That is the brake. I would just project on the hill, so gravity supplies $+50 g \sin 25^\circ$. Friction supplies $-50 g 0.05 \cos 25^\circ \sin 25^\circ$. The brake supplies $-260$. Add them up and you have the resultant.
Aug
13
comment What should the brake force in this problem be?
The braking force is applied to the particle. There is no coefficient to apply. (What is CoE?) The friction coefficient is used to convert the downward force due to gravity to lateral friction force, but if the brake apply 260N to the particle that is the force.
Aug
13
comment What should the brake force in this problem be?
If you are using $\mu$ for the coefficient of friction, as I read the problem it should not apply to the braking force. You say the brake exerts $260$N, so that is the force. It doesn't say how it is applied, nor does it matter.
Aug
12
answered What should the brake force in this problem be?
Aug
12
comment Thermodynamics about turbines
@apnorton: This is a Physics question. You are correct that it will be closed in a heartbeat if migrated. It will only land back here if OP is intransigent. I participate on both sites and prefer our homework policy, but this question supports the motivation for theirs-they get many more plug and chug than we do.
Aug
8
answered Weight added to truck
Aug
7
comment Is most of the matter in the observable universe within galaxies?
This NASA page quotes 4.6% atoms, 24% dark matter, 71.4% dark energy which has much less baryonic matter than suggested here. I believe this is more in line with current consensus science.
Jul
27
answered Do matter and antimatter annihilate or release energy?
Jul
25
answered What happens to a radioactive element or isotope's electrons when it undergoes alpha decay?