All Questions
30
questions
1
vote
1
answer
41
views
Work using angle vs. displacement [closed]
I am trying to calculate the work done on this wheel as it undergoes one full revolution, and is rolling without slipping.
I am aware that work can be calculated either using the integral of force ...
- 21
2
votes
2
answers
197
views
Why is the gravitational potential energy lost not subtracted from the required work done in the given problem? [closed]
An elastic string of natural length $l \;\text{m}$ is suspended from a fixed point $O$. When a mass of $M \;\text{kg}$ is attached to the other end of the string, its extension is $\frac {l}{10} \;\...
- 175
1
vote
1
answer
338
views
Can average power be non zero, but instantaneous power be zero
Q. A wind-powered generator converts wind energy into electric energy, Assume that the generator converts a fixed fraction of wind energy intercepted by its blades into electrical energy. For wind ...
- 125
0
votes
1
answer
34
views
Does this vector need to be fixed for the kinetic energy to be constant?
I was solving the following homework problem:
A force $\vec{F} = \vec{k} \times \vec{v}$ is applied to a particle of mass $m$. Here $\vec{k}$ is a fixed vector and $\vec{v}$ is the velocity of the ...
- 207
1
vote
1
answer
812
views
Work done for conservative forces is path independent Proof
So I’m looking at the proof for work that is path independent.
There is a line were the integral
Partial derivative V dr from r1 to r2 becomes
Partial derivative V r’ dt from t1 to t2
I’m a bit ...
0
votes
1
answer
261
views
Taylor Example 4.8. Is my reasoning sound? [closed]
This problem has been giving me all sorts of fits. For one, Taylor states that because the frictional force and normal force are forces of constraint, they produce no work. I'm trying to figure out ...
0
votes
2
answers
122
views
Is work done by the normal reaction force when an object is dropped on the ground?
When a perfectly non elastic object (let's say a book) is dropped on the ground, it's kinetic energy from the fall is transformed into heat and sound.
Now, if W = Fs, the work done by the normal ...
- 5
1
vote
1
answer
72
views
Variable Exchange $F(t) \to F(x)$? I want the value of the work done by drag [closed]
I got a nonlinear equation, which describes the magnitude of a force as a function of time, but I don't know how to calculate the work done by the force. Given:
$$F(t) = kv(t)$$
with
$$v(t)= \left(1-\...
3
votes
2
answers
608
views
Net Work Done When Lifting an Object at a constant speed [duplicate]
I am confused about the amount of work done when lifting an object at a constant speed. If you find the work done by you on the object and the work done by gravity on the object and add them the net ...
- 43
-1
votes
1
answer
483
views
The work done by emptying a well full of water upto a certain height [closed]
Lets say we have a well full of water (For now lets say it is cylindrical) .Lets say its height is $h$$well$. The water is filled upto a height $h$$water$. The radius of the well (cylindrical) is $r$ ....
- 307
1
vote
2
answers
50
views
Calculating work done vs. calculating final energy [closed]
I'm trying to solve for work after 2 seconds given $v(t)=3t^2$ and mass$=1kg$. There are 2 approaches:
Just calculate kinetic energy after 2 seconds: $E_k=.5*mv^2 = .5 *1 * (3*2^2)^2 = .5* 144 = 72J$
...
1
vote
2
answers
376
views
Why is the work done by a block into a spring the same from the work done by the spring on the block?
In the following situation:
A 700 g block is released from rest at height h 0 above a vertical
spring with spring constant k = 400 N/m and negligible mass. The block
sticks to the spring and ...
- 493
-1
votes
1
answer
48
views
Pendulum speed at angle $\phi $, expressing $d\vec{l}$ in terms of angle [closed]
Problem statement: Pendulum swings at angle $\phi = \phi_{0}$ , and $v_{\phi_0} = 0$. We want to find the velocity when it swings at an angle $\phi$.
Attempt at problem: By work energy theorem $$ \...
- 157
2
votes
1
answer
93
views
Conservation of energy with friction on a pool ball
I have a problem where I am given the mass $m$, radius $r$ and friction $\mu$ between a pool ball and table. The ball is not initially moving but at $t=0$ is struck by an impulse
$$p=\int_{-\epsilon}^...
- 33
1
vote
3
answers
5k
views
Concept of work done by spring
While deriving work done by spring force, our main problem is we cannot take out ${\bf F}$ vector out of the integral because it is not constant.
Hence we adopt the following method-
Considering a ...
- 329