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Apr
13
comment Help calculating work done by stretching a wire
It ain't just a typo when the answer was totally wrong. Thanks for correcting.
Apr
12
comment Help calculating work done by stretching a wire
Check your units. Force and Energy shouldn't have the same units. If $k=\frac{E S}{L_0}$ then $W=\frac{1}{2}k x^2$ and not $W=k x$
Apr
12
reviewed Edit What is the reason behind band gap narrowing in semiconductors
Apr
12
revised What is the reason behind band gap narrowing in semiconductors
added 94 characters in body
Apr
12
comment Truck driven from a small motor that can carry a heavy load, yet can travel fast.
FYI - Use the equations in physics.stackexchange.com/a/15620/392 to model the motion of the truck.
Apr
12
comment Truck driven from a small motor that can carry a heavy load, yet can travel fast.
Try Engineering
Apr
12
comment Truck driven from a small motor that can carry a heavy load, yet can travel fast.
Is the competition to a set distance, or set time?
Apr
12
answered How to interpret that forces do not depend on acceleration?
Apr
12
comment Is there any such thing as a change in acceleration (ex: 3 m/s/s/s)?
In valvetrain design engineering areas of linear snap (constant pop) are used as design limits for valve lift profiles.
Apr
12
comment Help calculating work done by stretching a wire
You start by deriving the force as a function of extension and then $W=\int F(x)\,{\rm d}x$
Apr
11
comment Clarify an assertion on torques from the Feynman lectures
It must mean forces that result in torque. A force trhough the center of mass isn't a force for rotation.
Apr
10
comment Rolling in V shaped groove
Check for slipping when $F \gt \mu N$. When slipping occurs $\alpha \ne \frac{a}{h}$ and you have both $a$ and $\alpha$ as unknowns, but $F$ is known. In the end you still have 3 equations and 3 unknowns.
Apr
10
comment Rolling in V shaped groove
Notice that I am glossing over some sign convetions (positive rotation ,etc) but the end result is the same.
Apr
10
comment Rolling in V shaped groove
I do implicitly account for no slip by $\alpha = \frac{a}{h}$. If the velocity at AB is zero it sets the kinematic relation of $v-\omega h = 0$ which I differentiate to get $a - \alpha h = 0$
Apr
10
answered Clarify an assertion on torques from the Feynman lectures
Apr
10
comment Clarify an assertion on torques from the Feynman lectures
I am surprised to see Feunman talk about net torque without discussing the point at which torques are measured about. For bodies in balanace, yes the point is irrelevent, but in general it makes a world of difference.
Apr
10
comment Clarify an assertion on torques from the Feynman lectures
See relavent answers to related questions physics.stackexchange.com/a/111348/392 and physics.stackexchange.com/a/93742/392
Apr
10
answered Rolling in V shaped groove
Apr
9
comment Confusion about average force applied over a time interval
If a pellet bounces off then the total momentum change is double of what it is if the pellet stops.
Apr
9
comment Confusion about average force applied over a time interval
Oh, I edited the answer then.