In physics, the kinetic energy of an object is the energy that it possesses due to its motion.
It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. Having gained this energy during its acceleration, the body maintains this kinetic energy unless its speed changes. The same amount of work is done by the body when decelerating from its current speed to a state of rest.
In classical mechanics, the kinetic energy of a non-rotating object of mass m traveling at a speed v is
1
2
m
v
2
{\displaystyle {\begin{smallmatrix}{\frac {1}{2}}mv^{2}\end{smallmatrix}}}
. In relativistic mechanics, this is a good approximation only when v is much less than the speed of light.
The standard unit of kinetic energy is the joule, while the English unit of kinetic energy is the foot-pound.
Hi!
I search the way to calculate the average orbital kinetic energy like is given in :http://physics.nist.gov/cgi-bin/Ionization/bun.php?Id=AlI (here is for aluminum).
I would like use the underlying method to calculate the average orbital kinetic energy for the silicon (Si) element.
If you...
Homework Statement
A proton has a speed of 0.2c. Find the speed of an electron that has (a) the same kinetic energy as the proton, and (b) the same momentum as the proton.
Homework Equations
K=ϒmc^2-mc^2
The Attempt at a Solution
This is what I did for the same kinetic energy part, but I...
The alarm at a fire station rings and a 71.3-kg fireman, starting from rest, slides down a pole to the floor below (a distance of 3.63 m). Just before landing, his speed is 1.42 m/s. What is the magnitude of the kinetic frictional force exerted on the fireman as he slides down the pole?
Givens...
1. The problem: A hockey puck is hit on a frozen lake and starts moving with a speed of 11.6 m/s. Five seconds later, its speed is 7.4 m/s. What is its average acceleration? The acceleration of gravity is 9.8 m/s. Answer in units of m/s. What is the average value of the coefficient of kinetic...
Hey guys, I need help with the following question.
A lead ball of specific heat capacity 130J/KgK travels with a speed of 100m/s before it hits a wooden cube fixed to floor and gets stuck inside.What will be the rise in temperature of this lead ball by the time it comes to
I attempted the...
Homework Statement
For my Physics lab this is what my teacher handed me... I have no idea how to attack the situation, can someone help solve?
Devise a procedure for an experiment which will measure the coefficient of kinetic friction between a block of unknown mass m and the table, where the...
Hi everyone, I've been systematically working through the exercises in my first year college textbook and have come up confused over this particular problem. I have a solution manual but it solves this problem differently than I did, though comes up with a similar answer. I've included my...
Homework Statement
Two identical spheres A and B are kept on a smooth surface. They are given the same impulse I. The lines of action of impulses pass through the center of A and away from the center of B. Then:
(A) linear kinetic energy of B will be less than that of A. (B) B will have...
The equation for momentum (potential energy) is PE=M*V.
The equation for kinetic energy is KE=(1/2)*(M*V^2).
You will notice that PE is the derivative of KE. and then you might add that M, simply Mass, is the derivative of PE.
However, because M is simply a scalar quantity, and the other...
Homework Statement
I'm actually making up my own problem here to try to resolve some confusion I'm running into on understanding kinetic energy and reference frames...
Let's launch a potato of mass m (just call it 1) horizontally with a potato gun on a fast vehicle moving 50 m/s, while I'm...
I was just wondering: why does lower kinetic temperature imply population inversion? I've read this is true in a few (astrophysics) texts regarding molecular clouds, although this seems to be a more general result that I haven't really read an entire explanation for. Nevertheless, do you have...
Homework Statement
A small block is on the point of slipping down a rough ramp inclined at 35 degrees to the horizontal.
a) What is the coefficient of static friction between the block and the ramp?
Answer μ_s = 0.70
b) The ramp is attached to the edge of a 0.8 m high table. After the block is...
Homework Statement
The position of an object of mass 2 kg is changing as a function of time by the formula x(t) = 4t^3-6t. (a) find the work done by the forces acting on the particle between t=1 and t=3s. (b) What is the object's velocity when the force on it is zero?
Homework Equations
is...
I am really confused here. I have studied that if the kinetic energy of a moving body is not changing then the net work being done on the object is equal to zero. But when we are talking about a body moving upwards at constant velocity there is no change in its kinetic energy but there is still...
I'm confused; forgive me if this dumb.
I'm trying to reason what "force" is, on a molecular level. I'm only concerned about normal forces here (pushes and pulls), not field forces. Forces in Newtons are vector quantities and only represent relationships between two things right? It isn't...
Homework Statement
In a lab assignment we created a Fletcher's trolley system and were asked to calculate the normal force, the force of friction, and then create a graph of both to find the coefficient of kinetic friction.
So far, the variables I have are:
Hanging mass: 0.100 kg
Sliding...
Hello everybody,
A special problem constrain me to make a variable change in my Hamiltonian operator, so with the kinetic energy operator, I have a doubt.
The variable change is: ## \theta \longrightarrow (\theta + k) ## (where ##k## is a constant).
And the kinetic energy operator...
"KE=3/2nRT=3/2kT" is applicable to only monatomic gas or all kind of gas?
What about " KE=1/2*fkT" ? (f: degree of freedom) Is it implies the same thing as "KE=3/2nRT=3/2kT" ?
Thank you.
It is my understanding that to calculate the change of kinetic energy of an object that speeds up from vi to vf you use this formula:
Change of kinetic energy = 1/2 * m * (vf2 - vi2)
When the initial velocity is 0 m/s I have no problems, but let's say an object that weighs 2 kg speeds up from...
College-level introductory physics textbooks usually devote a chapter to special relativity. Peter J. Riggs in his article appearing in the February 2016 issue of The Physics Teacher (pp 80-82) derives a couple of expressions for the kinetic energy of a massive (as opposed to massless) particle...
Homework Statement
A small block of mass 1.74 kg rests on the left edge of a block of length 3.05 m and mass 7.95 kg. The coefficient of kinetic friction between the two blocks is 0.279, and the surface on which the 7.95 kg block rests is frictionless. A constant horizontal force of magnitude...
basically, as far as I know we can derive 1/2mv2 from
∫F⋅ds=1/2mv2=(p2)/2m
for wave equation we use Hamiltonian H=P2/2m+V where P and V are both operators
However, I wonder how we can say that P2/2m is the term for kinetic energy because
∫F⋅ds=∫(dp/dt)⋅ds=1/2mv2 is saying that knowing F and...
On page 9 of *Quantum theory of many-particle systems* by Alexander L. Fetter and John Dirk Walecka, during the derivation of the second-quantised kinetic term, there is an equality equation below:
>\begin{align}
\sum_{k=1}^{N} \sum_{W} & \langle E_k|T|W\rangle C(E_1, ..., E_{k-1}, W...
Homework Statement
I have a bloc sitting on a horizontal table, and we shoot a ball through it. The speed right before entering the block is v and the speed when it exits the block is v/2. I need to prove that the fraction of the initial energy that is lost due to heat is 3/4 - γ/4, where γ is...
Homework Statement
A 1.40 kg block slides with a speed of 0.885 m/s on a frictionless horizontal surface until it encounters a spring with a force constant of 637 N/m . The block comes to rest after compressing the spring 4.15 cm.
Part A
Find the spring potential energy, U, the kinetic energy...
Homework Statement
You push a blob of gelatin with a constant force of 2.4 F across a wet table on which it slides easily. Because the blob shape distorts, its center of mass moves only 33 mm during the time interval in which the point of application of your force moves 53 mm .
By how much does...
Homework Statement
Two 0.50-kg carts are pushed toward each other from starting positions at either end of a 6.0-m low-friction track. Each cart is pushed with a force of 2.9 N , and that force is exerted for a distance of 1.0 m.
What is the kinetic energy of the center of mass of the system...
Homework Statement
In solid state physics,we know all the states of free electrons can be expressed by the First Brillouin Zone. We know the $$E(k+K)=E(k)$$ where K is reciprocal lattice vector. We also know that the kinetic energy of the electron is $$E_{k}=\frac{\hbar^2k^2}{2m}$$. [/B]...
I have read Average translation kinetic energy is 1/2RT per degree of freedom and Average translation kinetic energy for an ideal gases is 3/2RT.How? Does it imply f=3 for all ideal gases?
I saw another post about this but i didn't quite find what i was looking for there so i thought i'd give it a go instead with a thread.
Homework Statement
Calculate the exact value of the kinetic energy of the hydrogen atom in its ground state. No more information is given, we are referred to...
Homework Statement
A 120 kg hoop rolls along a horizontal floor so that its center of mass has a speed of 0.240 m/s. How much work must be done on the hoop to stop it?
Homework Equations
I of hoop=MR^2
The Attempt at a Solution
KE=0.5*m*v^2+0.5*(mR^2)(v/R)^2...
Hi
I'm in high school but what I'm going to ask you is probably being teached in college.
General formula: p=(2/3)*(N/V)*Ek
p- pressure
N- amount of molecules
V- volume of the container
Ek - AVERAGE kinetic energy
I've been told by my physics teacher, that 2/3 constant factor in kinetic theory...
Homework Statement
A.What is the change in kinetic energy of the crate? Answer in units of J.
B.What is the speed of the crate after it is pulled 5.79 m? Answer in units of m/s
Magnitude of work done by gravity= 200.786
Work done by applied force= 822.18
mass=8.91kg
force pulling on box= 142N...
Homework Statement
A 410 g particle in a semi-spherical bowl of radius 0.9 m is released from rest at point A at the level of the center of the bowl, and the surface of the bowl is rough. The speed of the particle at B is 2.6 m/s. The acceleration of gravity is 9.8 m/s 2 . What is its kinetic...
Homework Statement
Hi, we had a Lab Activity on the Coefficient of Friction, but right now I am really confused and stuck. Since the teacher used an online resource, we are supposed to make two graphs based off the data and it's very unclear and unhelpful. :( I can't seem to find anything at...
I am trying to find the most efficient way to convert kinetic energy to heat. The first thing I know is friction, however friction cause wearing for long term use. The second is convert to electric energy(dynamo) and then convert to heat using electric coil, however I think that has low...
Homework Statement
Consider a gas of molecules of mass m at equilibrium at temperature T. Obtain an expression for the fraction of molecules having kinetic energy e = 1/2mC2 in the range e to e + de.
This is problem 5.3, page 48 of Vincenti and Kruger's Intro to Physical Gas Dynamics
Homework...
Homework Statement [/B]
An ice skater executes a spin about a vertical axis with her feet on a frictionless ice surface. In each hand she holds a small 5kg mass of which are both 1m from the rotation axis and the angular velocity of the skater is 10rad/s. The skater then moves her arms so that...
I've added 'in classical physics' in the thread title because all the differences between them that I found on the internet involved relativistic physics. It was something like both momentum and kinetic energy being components of a four-momentum or something like that. But I cannot understand...
Homework Statement
A disk of mass m1 is rotating freely with constant angular speed ω. Another disk of mass m2 that has the same radius is gently placed on the first disk. If the surfaces in contact are rough so that there is no slipping between the disks, what is the fractional decrease in the...
From Chris' perspective Bob is traveling with 1.5*108 m/s in direction a. Angelica is also traveling with 2.4*108 m/s in direction a.
From Bob's perspective Chris is traveling with 1.5*108 m/s in direction b (The opposite of x). Angelica is traveling with 1.5*108 m/s in direction a.
They all...
Homework Statement
A child slides down a slide with a 28 degree incline , and at the bottom her speed is precisly half what it would have been if the slide had been frictionless. Calculate the coefficient of kinetic friction between the slide and the child.
Homework Equations
Newtons second...
Homework Statement
A child slides down a slide with a 28° incline, and at the bottom her speed is precisely half what it would have been if the slide had been friction-less. Calculate the coefficient of kinetic friction between the slide and the child.
Knowns:
28°
speed=V/2
Homework Equations...
I'm having a bit of trouble conceptualizing this. I've looked all over the Internet, and I've been seeing that in completely inelastic collisions the reason that kinetic energy is not conserved is because energy goes into deformation, sound, propelling shrapnel, and especially heat (among other...
Homework Statement
I have the decay
K+ → μ+ + νμ
Calculate:
1. Momentum of μ+
2. Total energy of νμ
3. Mass of K+
4. Speed of μ+
5. Speed of νμ
Homework Equations
The only thing we get are the kinetic energy of μ+ so Kμ+ = 152.53 MeV
and the mass of mμ+ = 105.658 MeV/c2
The Attempt at a...
https://scontent-dft4-1.xx.fbcdn.net/v/t35.0-12/14796269_10210868496286479_1115393743_o.jpg?oh=0ccd692c60a1d0bab84d5fbaf7e6197b&oe=580A1894
In the figure, a 6-kg box is sliding up an incline that makes an angle of theta=30 degree (with respect to the horizontal). As it slides up the incline, a...
Homework Statement
Not actually a homework question but is an exercise in my lecture notes.
Homework Equations
I'm following this which demonstrates that the momentum operator is Hermitian:
The Attempt at a Solution$$KE_{mn} = (\frac{-\hbar^2}{2m}) \int\Psi_{m}^{*} \Psi_{n}^{''} dx $$
$$...
Homework Statement
a 10 kg box is moving on a level floor. The coefficient of static friction between the box and floor is 0.3. What is the force of kinetic friction?
Homework Equations
fk = FN * μk
The Attempt at a Solution
I rearranged the formula so that everything was set equal to the...
Homework Statement
A bead slides on a wire, which is in a vertical plane, as shown in the diagram. Gravity acts in the -y direction. The bead starts at A, moving to the right with an initial velocity v. The wire is frictionless between A and D and between F and G, but there is friction between...