All Questions
70
questions
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0
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47
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Work a medium of energy conversion? [duplicate]
Is work a medium to convert one form of energy to other? i.e. to say without work you can't convert type of energy?
Similar type of question pertains to heat.heat is also medium of conversion of ...
- 11
0
votes
2
answers
126
views
How to derive $dW = dE$? [closed]
From the definition of power:
$$P \ = \ \frac{dW}{dt} \ = \ \frac{dE}{dt}$$
Multiplying both sides by $dt$, we get:
$$dW = dE$$
$1.$ What does this imply?
$2.$ Are there any other (perhaps more ...
- 485
4
votes
7
answers
634
views
Why does incline on treadmill burn calories faster?
So I was at the gym today, running on the treadmill, when the question hit me:
If I run with the treadmill on incline, I burn more calories. Since I run at the same speed, kinetic energy is constant, ...
- 163
1
vote
2
answers
439
views
Why is the work done by friction zero when body is rolling? [duplicate]
Why is the work done by friction zero when body is rolling? Does it mean no energy is dissipated by friction.
0
votes
1
answer
833
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Formula for Power from Kinetic Energy
Work Done = $Fd$
Power = $Fv$
If the (net) Work Done = Change in Kinetic Energy, and the object starts from rest:
Work Done = $\frac{1}{2} mv^2$
Power = $\frac{1}{2} m av$
Power = $\frac{1}{2} ...
- 395
1
vote
1
answer
68
views
Does measured mechanical power and work change between inertial frames?
Imagine a car A is accelerating.
Two observers at constant speed, B and C, analyse the change of A's kinetic energy over a same time interval.
B sees A going from 10 to 30 m/s
C sees A going from ...
- 223
2
votes
2
answers
314
views
Why frictional force does no work on the car?
Question statement from David Morin's Classical Mechanics :
The friction force from
the ground on the tires is what causes the car to slow down. But this force
does no work on the car, because the ...
- 885
0
votes
2
answers
8k
views
Energy dissipated by friction vs Work done by friction
Is energy dissipated by friction the same as work done by friction where the equation is W(friction) = Ff * d cos theta .
However, since work is the transfer of energy and not energy itself then is ...
- 31
1
vote
0
answers
76
views
Conceptual Difficulty About Work
So my issue is best explained with an example.
Let us consider a ring of mass $m$ and radius $R$ sliding down an incline of angle $\theta$ ($I = mR^2$). It starts from a height h, and we wish to ...
- 11
-1
votes
1
answer
58
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Conservation Of Mechanical Energy [closed]
I just observed that ,
Mechanical Energy(E) = Potential Energy(U) + Kinetic Energy(K)
Now ,
from simple algebra,
E-U=K
Also we know that Kinetic Energy K is always positive.
I ...
- 564
1
vote
2
answers
163
views
Relation between field and Potential energy of a body
I have read that if a body is in a field and is
1. moved in a direction opposite to the direction of a field, its potential energy increases.But why does it increase?
2.Also, if we move the body in a ...
- 597
1
vote
1
answer
696
views
Why does holding an object cost energy while no work is being done? [duplicate]
I was reading the discussion here:
Why does holding something up cost energy while no work is being done?
I feel as though the question is being avoided.
Suppose instead of holding an object by hand ...
- 21
-1
votes
2
answers
240
views
I dropped my tissue box on a glass table, the box didn't bounce back, table didn't move nor break, what happened?
I have a box, it drops and thus by moving has Kinetic energy, It doesn't penetrate and impacts however the box doesn't rebound nor breaks the table. Its like when I slam my fist on a table but the ...
- 67
4
votes
2
answers
599
views
Work done changes between reference frames?
(This is not homework; a friend shared with me this puzzler and neither of us can figure it out.) Suppose you are in a plane traveling at velocity $v_1$ relative to the ground. The flight attendent ...
- 43
5
votes
2
answers
2k
views
Why does the work-energy theorem need to include internal forces?
Can anyone kindly explain me why work energy theorem must also include internal forces?
The proof of work energy theorem is derived from Newton's laws of motion, but Newton's laws of motion don't ...
- 399