Tagged Questions
0
votes
1answer
52 views
Short-duration forces
In circular motion, it is said that the centripetal force acts only for a very very short period of time, hence is able to only change the direction but not magnitude of the velocity.
Similarly in a ...
0
votes
1answer
64 views
Work done by Static friction
Here $v1$ is relative to the block on which sphere is pure rolling but static friction isn't $0$ as of now .
In the following diagram, is work done by static friction $0$ ?, since the point of ...
1
vote
2answers
152 views
Centripetal Force Acceleration
Suppose you want to perform a uniform circular motion . Then a body performing uniform circular motion horizontally needs an acceleration $= \frac{v^2}{r}$ at each point on the circular path with ...
0
votes
0answers
50 views
Work And Energy Question [closed]
$H = 3\text{ m}$,$m=2\text{ kg}$
The right side is rough.
I want to figure:
what is the coefficient of friction $\mu$?
How high and exceed the maximum return on the plane right body?
I know ...
-6
votes
4answers
365 views
Violation of Newton's Second Law (?)
Here the big circle denotes the circular path of a stone(small circle on path) tied to a string from the centre of the circular path .
This is COMPLETELY HORIZONTAL
At an instant the velocity in ...
0
votes
0answers
36 views
What is the total work done in this problem? [closed]
A 1800 kg trick airplane is 450 m in the air. At this point the plane takes a dive
with an initial speed of
42 m/s and accelerates to 64 m/s, dropping
a total distance of 120 m.
(a) Using the ground ...
0
votes
1answer
91 views
Energy needed to lift and bring down an object
A mass of 0.5 Kg needs to be moved from point A to another point (B) which is 1 meters above point A. The time for this movement should be 0.2 seconds, then the mass is kept at position B for another ...
1
vote
1answer
114 views
Work done by friction
Suppose we have a block of mass $M$ and we are moving it up a curve, very slowly ($a=0$). The surface is not smooth, and coefficient of friction is $\mu=\mu_s=\mu_k$.
To move the block we apply a ...
2
votes
1answer
149 views
How to understand the work-energy theorem?
How to understand the work-energy theorem?
I took a short lecture on physics for engineering last week. The lecturer emphasized that the work done on an object will cause the kinetic energy change as ...
0
votes
1answer
69 views
Why work to change velocity from 0 to 20 km/h is less then from 20 to 40? [duplicate]
Imagine spaceship in vacuum with mass = 1. At beginning, it has velocity 0, and kinetic energy 0.
$$W_1 = 0$$
Then, it turns on its engine, and changes velocity from 0 to 20 (delta v = 20). It's ...
1
vote
1answer
74 views
Work as an integral of mass over velocity?
As I've understood it, the area under $F$-$s$-graph is the work done, so then :$$W(s)=\int{F(s)ds}$$
I am also given this equation ($W_k$ is kinetic energy, which is equal the work done to set the ...
0
votes
0answers
27 views
How did scientists come up with Work? What was it fundamentally defined as? [duplicate]
Now before I get into the questions I want to make a couple of things clear, I know that there were similar questions like this and I've been through (what i think is) all of them and none of the ...
1
vote
2answers
143 views
Finding maximum speed in a work-energy problem
I have the following problem:
The Royal Gorge bridge over the Arkansas River is $310\text{ m}$ above
the river. A $57\text{ kg}$ bungee jumper has an elastic cord with an
unstressed length of ...
3
votes
2answers
120 views
Find work done by force along a path - is parameterization the only way?
$F = x^3y^4 \hat i + x^4y^3 \hat j$ from $(0,0)$ to $(1,1)$.
I am given different paths.
For example, "first along x axis and then along the y axis" is one of the paths.
Is this problem solvable ...
3
votes
3answers
119 views
When can one write $a=v \cdot dv/dx$?
Referring to unidimensional motion, it is obvious that it doesn't always make sense to write the speed as a function of position. Seems to me that this is a necessary condition to derive formulas ...
4
votes
2answers
122 views
Conservative Force and $1/r^2$
Does the inverse square law have anything to do with conservative behavior of the central forces?
1
vote
1answer
151 views
Work done in projectile motion
A projectile is shot at some inclination to the ground. It falls at another point having R distance from the initial point on the ground. Is there any work done?
If initial velocity vector is $(u\cos ...
7
votes
3answers
554 views
Is the normal force a conservative force?
Most of the time the normal force doesn't do any work because it's perpendicular to the direction of motion but if it does do work, would it be conservative or non-conservative?
For example, consider ...
-1
votes
2answers
348 views
Work done by the air resistance [closed]
A ball of mass 0.37 kg is thrown upward along the vertical with a
initial speed of 14 m / s, and reaches a maximum height of 8.4 m.
a) What is the work done by air resistance on the ball? b) ...
0
votes
1answer
132 views
Is resistance to motion directly proportional to the speed of a moving object?
Power is known to be equal to the force x velocity (P=FV).
Im solving a question that states the following :
Car with engine working at 32 kW, mass of 1 tonne, travels at a constant speed of 40m/s ...
1
vote
2answers
184 views
Mechanics Question: Energy, Work and Power
I'm a pure mathematician by trade, and have been trying to teach myself A-level mechanics. (This is not homework, it is purely self-study.)
I've been working through the exercises and have come up ...
2
votes
5answers
269 views
Is there a mathematical derivation of potential energy that is *not* rooted in the conservation of energy?
For simplicity I'll consider only gravity, but in general this question only applies to conservative forces.
As per my understanding, the way one gets to the equation for gravitational potential ...
1
vote
3answers
96 views
Mechanics Problem
I'm trying to follow Feynman's lecture. Unfortunately I'm a bit stuck on a small piece, so if you could show me what I'm doing wrong then I'd greatly appreciate your help. I want to exactly know how ...
-3
votes
1answer
82 views
Work done by an ideal, massless, inextensible, non-relativistic string [closed]
what is the work done by an ideal, massless, inextensible, non-relativistic string in an isolated system with respect to a reference frame at rest? If it is zero, then why?
2
votes
1answer
100 views
Moving along friction surfaces
If a particle moves along a one dimensional surface with constant friction. As the particle moves from point $A$ to point $B$ it loses an amount of energy equals $E(A,B)$. Consider that the particle ...
1
vote
2answers
305 views
Calculating force required to stop bungee jumper
Given that:
bungee jumper weighs 700N
jumps off from a height of 36m
needs to stop safely at 32m (4m above ground)
unstretched length of bungee cord is 25m
Whats the force required to stop the ...
0
votes
3answers
247 views
A chain 64 meters long whose mass is 20 kilograms is hanging [closed]
A chain 64 meters long whose mass is 20 kilograms is hanging over the edge of a tall building and does not touch the ground. How much work is required to lift the top 3 meters of the chain to the top ...
1
vote
2answers
230 views
Why is work defined as force dot displacement?
Why is work defined as force dot displacement? I know that it is defined like that based on the observational fact - we do more work when we apply greater force or move to a greater distance. But I ...
4
votes
5answers
2k views
Why there is a 1/2 in kinetic energy formula? [duplicate]
Possible Duplicate:
Why is there a $\frac 1 2$ in $\frac 1 2 mv^2$?
Hèllo, I have a question about kinetic energy formula.
As you know, in kinetic energy formula, we have:
...
2
votes
3answers
960 views
How do I find work done by friction over a curve represented by a polynomial?
I am facing a problem in Physics.
Problem: What will be the work done by the frictional force over a polynomial curve if a body is sliding on this polynomial($a+bx+cx^2+dx^3+\ldots$) curve from rest ...
1
vote
3answers
108 views
Carrying water on person, or on the frame when bicycling
So, the question is as follows:
What is the difference in work exerted by the rider in the two following scenarios?
a) Rider + bike. Water carried in a holder on the frame
b) Rider + bike. Water ...
3
votes
1answer
341 views
I have a slight problem understanding the concept of “work”?
What I understand is that work is not the same as a car using gas or a crane lifting a car high up into the air. Let's use the crane as an example. And let me write out a few lines from the book.
...
2
votes
1answer
380 views
Does moving something horizontally in gravity do no work?
Bill’s job is to lift bags of flour and place them in the back of a
truck, which is parked next to him. Sally is loading the same bags of
flour into a similar truck that is located 10 m away. ...
1
vote
2answers
559 views
Why is there a $\frac 1 2$ in $\frac 1 2 mv^2$?
For elastic collisions of n particles, we know that momentum in the three orthogonal directions are independently conserved:$$ \frac{d}{dt}\sum\limits_i^n m_iv_{ij} =0,\quad j=1,2,3$$
From this, it ...
2
votes
1answer
116 views
Work Done to click a mouse?
Is there any good research done to find out the work done in clicking a mouse button.
any link to that would be greatly appreciated.
P.S.
i am not too sure whether this question belongs here or ...
3
votes
1answer
307 views
A Question about Virtual Work related to Newton's Third Law
In describing D'Alembert's principle, the lecture note I was provided with states that the total force $\mathbb F_l$ acting on a particle can be taken as,
$$\mathbb F_l=F_l+\sum_mf_{ml}+C_l,$$
...
1
vote
1answer
306 views
Work and Area under a Curve relating to Hooke's Law
If it takes work W to stretch a Hooke’s-law spring (F = kx) a distance d from its unstressed length, determine the extra work required to stretch it an additional distance d (Hint: draw a graph and ...
