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.
In definition and proof of kinetic energy, it uses the second law of Newton. The length of the box is L and it uses this length to define the time of applying the force on the wall. Actually this time should be only time that molecule reaches to the wall and changes its velocity.
My question...
1200lb total vehicle weight
800lb total flywheel mass [4x200ea]
Diameter 18.75"
Flywheel RPM 3500 [120v electric motor plugged into wall]
Pulley to drive wheel at 1:1 [6"pulley] or to 12' pulley
Please help write the end of this story before I start. This is a "rev up" car built for...
I am proposing a piece of equipment a bit similar to Crooke's radiometer with the aim of using kinetic motion of air particles to rotate the mill, without need for an external source of EM radiation.
Instead of flat vanes as in Crooke's radiometer, I propose 3-dimensional vanes in the shape of...
If I place an insulated container of gas on the edge of a turntable and then rotate
the container as a constant angular velocity, what happens to the gas?
Does the temperature of the gas increase? If so, how was work done on the gas?
The more I think about it the less clear the respective natures of kinetic energy and potential energy (and of their sum, the so-called total energy) become. The thing is I have the impression that once you try to go a bit further than the usual description of "scalar values assigned to systems...
Hi All,
Perhaps I am missing something. Schrodinger equation is HPsi=EPsi, where H is hamiltonian = sum of kinetic energy operator and potential energy operator. Kinetic energy operator does not commute with potential energy operator, then how come they share the same wave function Psi? The...
Homework Statement
Multiple choice question:
The momentum of a body has increased by 25%, then its kenitic energy will roughly increase by...
1. 25% 2. 5% 3. 38% 4. 56% 5. 65%
Homework Equations
Pl = mv (Pl is the momentum, m is mass and v is velocity)
K.E = 0.5 mv^2
The...
Can there be a system that utilizes mechanical energy to produce kinetic energy, but "storing" the mechanical energy to be used at a different time for kinetic energy? Like a bike where you pedal but don't move; that mechanical energy is waiting to be "released" by some mechanism
*** exclude...
Hello. I'm looking for a purely physical explanation for an unusual event that occurred in my home. The circumstances are humorous and creepy and cause for speculation concerning the paranormal. However, I believe we have identified the true cause of the phenomenon and want to vet it against...
Homework Statement
A hydrogen atom collides with another hydrogen atom at rest. If the electrons in both atoms are in the ground state, what is the minimum kinetic energy of the hydrogen atom such that the hydrogen atom at rest will have its electron in the first excited state after collision...
K= ∫mvdv = ∫m dx/dt dv = ∫m dx/dv dv/dt dv = ∫m dv/dt dx = ∫Fdx = U
=> K=U, why isn't this true? If it is, wouldn't that mean that Kinetic Energy is always equal to Potential Energy?
Why so?
Quoted from Quantum Physics 3rd ed. by Stephen Gasiorowicz, p. 26.
It was explaining why we ignore the terms with exp[iwt] when adding plane waves to form a wave packet:
I've been working on this problem for a while and here comes the problem: I'm building a balancing system for a bicycle using Gyroscopic effect (take a look at Figure 2 for more details). My system consists of 2 parts:
the bicycle itself
a flywheel on top of it
All parameters are given. The...
Homework Statement
Problem: http://imgur.com/a/Sw2zA
Hi all,
I was given this problem as homework and I have almost no clue on how to solve it. I have tried for some time with no luck.
Homework Equations
We learned about kinetic and potential energy as well as work.
W = F*d
W = delta KE
PE =...
Hi guys. I'm new to this forum so I'm not sure if I'm posting this in the right place or correctly, but I was totally stumped on a Physics 12 question as I was studying for my exam.
The question is:
An explorer spacecraft is descending towards Mars using a rocket engine for braking. The...
Homework Statement
The decomposition of phosphine 4PH3(g) + P4(g) + 6H2(g) is first-order with respect to phosphine with a rate constant k = 0.0155 s-l at 953 K. If the decomposition occurs in a constant-volume batch reactor at 953 K, calculate, for 40% conversion of PH3,
(a) the time...
Homework Statement
5.5 MeV alphas hit Be-9 and produce carbon with a gamma. the Q value is 10.65
I have to find the kinetic energy of the carbon nucleus and the gamma and I am to ignore the gamma ray momentum.
Homework Equations
T = p^2 / 2*m
Q = T_be + T_alpha - T_c - T_gam[/B]The Attempt...
Homework Statement
A 5.72 kg block is released from rest on an inclined surface. The incline makes an angle of 25.0 degrees relative to horizontal. The block is known to be traveling at a speed of 1.33 m/s after sliding a distance of 2.60 m along the incline. How much work was done on the block...
Homework Statement
In our physics course, we were studying one dimensional waves in a string. There, our teacher stated that the kinetic energy in a small piece of a string is dK=\frac{1}{2}μdx\frac{\partial y}{\partial t}^2 were μ is the linear density of the string, so he claimed that...
Homework Statement
A child is initially sitting near the outer rim of a revolving merry-go-round. Suddenly, the child moves towards the center of the merry-go-round (while it is still revolving). For the merry-go-round+child system, let the symbols L and K refer to the magnitude of the angular...
Why are kinetic moments not included in the regular summation of the moments? In other words why is the equation ∑M = ∑Mk and not ∑M + ∑Mk = 0 ?
I guess it would help if someone could explain exactly what a kinetic moment is, and why it is equal to the summation of the moments due to external...
Homework Statement
This problem is from the 2015 AP Physics C Mechanics free response, question 3 part b.
https://secure-media.collegeboard.org/digitalServices/pdf/ap/ap15_frq_physics_c-m.pdf
Homework Equations
K = 1/2Iω2
U = mgh
The Attempt at a Solution
The potential energy of the bar when...
Why don't we include the kinetic moments in the summation of the moments of a rigid body? In other words, why are the kinetic moments on the opposite side of the equation as the moments due to external forces? I understand that the math works out but it's not making sense to me conceptually...
Homework Statement
Hi Guys, I don't have a particular problem that I need to solve but I need help with understanding a concept. So we agree that irrespective of mass of an object they will both fall at a same rate if there is no air resistance. However, why is it then when we increase the mass...
Homework Statement
A 1.0x10^3 kg elevator carries a maximum load of 800kg
Velocity = 3m/s
Distance = .01km
Net work = 13640J
Homework Equations
Force of friction = (m)(mu)(gravity)
The Attempt at a Solution
Gravity = friction
9.8 = (mu)(17640)
.001 = mu
Hello to All !
I have a question that Whenever an electron from bulk material trapped by a quantum well that electron's 3rd dimensional kinetic energy component vanishes, But where that goes, is it added to the other 2 dimensional kinetic energy components..?
Homework Statement
A child is playing with their Hot Wheel cars. They have set up a track which is initially horizontal but then ascends to a second horizontal section which is 50 cm higher than the initial track. The track is friction-less until the car reaches the upper section of the track...
Homework Statement
Consider an Ocean Current flowing at 2.5 m/s. a) How much energy is contained in a cubical block of water 1m on the side. (The density of the water is about 1030kg/m^3.) b) If the flow is perpendicular to one of the cube faced, what is the rate at which current flow carries...
If you have a U-shaped pipe like the attached image, with more fluid in the left column than the right, then the fluid will level out basically because of Pascal's Law. Force on the fluid is exerted on every part of it in equal direction etc..
So when the fluid levels itself it flows across to...
Question:
Calculate the kinetic energy required to accelerate a single proton from rest position to 0.9999c. The mass of the proton is 1.67*10^-27 kg.
Equations Used:
Ek=(mc^2/√ 1-(v^2/c^2))-mc^2
Attempt at the problem:
Ek=(1.67*10^-27kg)(3*10^8m/s)^2/√...
Homework Statement
What is the kinetic energy given to the proton in the decay of a neutron when:
a) The electron has negligibly small kinetic energy
b) The neutrino has negligibly small kinetic energy
Homework Equations
Q = (mn - mp - me - mv ) c2 = .782MeV
Where T is kinetic energy, and...
if i connect an electric current of 30 volts to argon gas to transform it to plasma, what is the average kinetic energy of the argon particles in that plasma?
Homework Statement
One effect of plate tectonics is that the North American continental plate moves across the Earth’s surface at a speed of about 1.15 cm/yr. The North American plate has an area of about 35 million square kilometers, an average thickness of about 25 km, and a density of about...
Homework Statement
A cylinder containing an ideal gas is in vertical position and has a piston of mass ##M## that is able to move up or down without friction (Fig. 13.2). If the temperature is increases,
...Fig (13.2)
(a) both ##p## and ##V## of the gas will change.
(b) only ##p## will...
Hi all,
I stumbled into a somewhat odd mathematical problem, so I guess I've overlooked an important detail.
If I have a mass of 1kg on wheels horizontally, and apply 10N of constant force so the mass is accellerating. I assume the velocity of that mass after 1 second is approx 10m/s. Then...
Hi everyone,
I'm having a difficult time figuring out this problem. Could someone give me some pointers? I set up the equations and the free body diagrams (hopefully they're correct) ; all I have to do now is solve for F.1. Homework Statement
A block of mass m is on top of a block of mass
M =...
A rocket is drifting in gravity-free space and is observed by an external observer who is also drifting at an unchanging location using an arbitrary coordinate system.
The rocket accelerates at a fixed rate using a massless photon engine that results in a negligible change in the mass of the...
Homework Statement
I am working on a problem similar to this one:
In this solution, I do not understand what mc is, can someone explain? Also, would I follow the same type of steps if I have the kinetic energy of a photon and I need it's wavelength?
Homework EquationsThe Attempt at a Solution
I am confused of how Work basically equals to Kinetic Energy...I will give an example just as way to help you help me get an idea about how it works...the example I thought of is... '' James (100 kg) jogs on a straight road at a constant velocity of 2.2 m/s for 600 seconds, how much energy does...
When doing work on the brakes of a car or bicycle, how much of that energy is actually removed from the total kinetic energy of the vehicle?
What is the most efficient braking system?
Sorry If the thread name confuse you.
I want to know if I want to find the Torque from deriving Kinetic Energy and the system has Object the Rotate and the rotating cause linear motion(v).
Let's say it a Rolling Disc on the non-slope plane which has angular velocity ω and that ω cause it to move...
Hello everybody,
My question today is:
Given a molecule that has an internal degree of liberty ( let's take the ethane molecule with its internal rotation as an example), how to write the kinetic energy operator by means of the corresponding internal coordinate?
Thank you guys.
Konte
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...