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.
Homework Statement
A 4.30 kg block is pushed along a floor by a constant applied force that is horizontal and has a magnitude of 43.0 N. The figure gives the block's speed v versus time t as the block moves along an x axis on the floor. The scale of the figure's vertical axis is set by vs =...
why we assume that velocity decreases linearly in a spring (i.e. if one end is fixed, then velocity of a particle (of spring) at x from fixed =vx/l where v is the velocity of the free end) and why does it hold good too when the spring (linear mass density) is non uniform...
EDIT: spring has...
Dear PF Forum,
I have a question in mind. But I'm not sure if this belong to SR forum, cosmology or classical physics.
So I post it here.
And perhaps as some of you might have known before or thought it over. It's about kinetic energy.
Supposed this...
A rocket, with a rest mass 1 ton.
And the...
I have a question regarding how to calculate kinetic energy. Let's say I was to find the kinetic energy of a ball shot at 180 m/s at a 45 degree angle. Do i simply sub in 180 as v (velocity) in the kinetic energy equation (1/2mv^2) or must it be split into components?
I've recently created a 3D motion generator (Anti-Gravity Transportation (AGT)) in 2D/3D design. unfortunately my current physics knowledge is not advanced enough to take this machine to its maxium potential. i can concieve perpultion and sustainable energy coming from this idea. my question...
We know that If object is homogenius and small (like gold atom) we can use this equation to calculate total energy of object when it moves very slow due to speed of light.And the equation is ##1/2(m_1v^2+m_2v^2+m_3v^2...=1/2Mv^2##, ##(M=m_1+m_2+m_3...)## here v is small and we are talking about...
Hi,
I'm reading a high school textbook about mechanics. It's amazing how the author draws up the problems and solves them by introducing a new consistent concept.
Now I'm reading about collisions. He writes the conservation of momentum but the problem is that we have two unknowns in one...
Hi all,
I'm brushing up on some thermodynamics, and having been reading up on the interpretation of temperature as derived from kinetic theory. I can follow the derivation for an ideal, monatomic gas which relates temperature to the average, translational kinetic energy of the molecules. Most...
I heard that proportionality of kinetic energy with square of velocity, ##E_k\propto v^2##, can be derived with help of quadratic forms.
It goes like: we guess that ##E_k\propto v^2## and we assume that momentum ##p\propto v##, then equation is valid in another inertial system. And so on. The...
Homework Statement
A crate on a rough horizontal floor is being moved horizontally by a force applied at a 16 degree angle above the horizontal. This is the smallest force that will move the crate at constant speed. What is the coefficient of kinetic friction?
A :
.11B :
.27 C ...
Hi all,
I'm trying to come up with velocity equations for a multi-enzymatic system and came across this velocity equation. Does anyone recognize this equation?
There was no citation or derivation and the variables were not explained. This is my guess:
P, Q, A, B are concentrations of some...
Homework Statement
A charged particle (q = -8.0 mC), which moves in a region where the only force acting on the particle is an electric force, is released from rest at point A. At point B the kinetic energy of the particle is equal to 4.8 J. What is the electric potential difference...
Considering horizontal flow in a pipe (under the action of pressure forces only) if we focus on a fluid element we have a pressure gradient across the same i.e, a net pressure force will always act over the element that essentially maintains the flow.Now, in a region in the flow field if the...
For particle in the box wave function, it is the eigenfunction of kinetic energy operator but not the eigenfunction of momentum operator. So, do these two operators commute? (or it has nothing to do with commutator stuff?)
How about for free particle? For free particle, the wave function is...
Dear PF Forum,
I'd like to ask a question regarding a post in Relativity sub forum.
The formula for kinetic energy is ##E_k = 0.5mv^2##
Which makes sense. Because if we push/accelerate 1 kg object for 1 m/s2 for 8 meters, we'll spend ##E = N.m = 8 joules##
How much time do we need to do that...
Homework Statement
[/B]
A 2.0 kg ball moving with a speed of 3.0 m/s hits, elastically, an
identical stationary ball as shown. If the first ball moves away
with angle 30° to the original path, determine:
a. the speed of the first ball after the collision.
b. the speed and direction of the...
Homework Statement
2. Homework Equations [/B]
KE=1/2 mv2
The Attempt at a Solution
To calculate the kinetic energy of the ball just after it leaves the surface, I use the ratio of the centre of gravities of the ball at the two different heights. My working is (0.41/0.76)×0.75 which gives me...
All particle species are in equilibrium at early times of the universe. But I didn't find any book that makes the difference of kinetic and chemical equilibrium clear. I have some of my own opinions and I hope to get your comments:
(1) kinetic equilibrium means the distribution function obeys...
Homework Statement
In the figure here, a block of ice slides down a frictionless ramp at angle θ=55.0 ˚ while an ice worker pulls on the block (via a rope) with a force that has a magnitude of 54.0 N and is directed up the ramp. As the block slides down through distance d = 0.400 m along the...
Homework Statement
I'm stuck on question A4 that is linked below. University won't provide me with any solutions. I have a TKP resit exam next month.
Homework Equations
dU=dQ-PdV
The Attempt at a Solution
Internal energy is equal to heat flow plus the work done. Work done is 0 because it's...
Imagine two experiments A and B.
In experiment A I load a gun with a cartridge and shoot a bullet. Total energy in this experiment will be E(heat) + E(projectile). I include recoil in E(projectile). E(heat) in its turn will heat the muzzle and some air. Done.
In experiment B I do...
This is mostly a conceptual confusion I'm having, not a specific problem, so it didn't seem like it'd fit under homework problems.
I'm having trouble understanding when potential energy should or shouldn't be used in a energy conservation equation. When looking at a problem with a skier going...
hi
I have been given an assignment at school to look at various ways heat is transferred through liquids. I'm interested in looking more into the kinetic energy of molecules and how their vibration causes heat, I would like to know if there is a device I could use to record the frequency of...
I know there are some threads discussing about the Lorentz force equation but this is something different I came across and I couldn't find anyway to derive that formula.
To be specific I'm talking about a charged particles in a magnetic field, where F=vqB and everything that is moving has...
There is 14 km of tunnel of 7.7 m diameter, full of water traveling at 3.75 m/s,that represents approximately 8000 Megajoules of kinetic energy.
How? Calculate it to prove (Taken From Wikipedia under topic of "Water Hammer".
Homework Statement
This is a theoretical question from my homework. We did a lab in class where we were using motion to see how kinetic friction is affected by different variables. We found the acceleration of a sliding wooden block (sliding on another wooded block), and then used that...
Homework Statement
A marble that is rolling without slipping approaches a hill at 8.5 m/s. How high vertically will the marble go under these circumstances:
If the hill is rough enough to prevent any slipping?
If the hill is perfectly smooth?
Why does the marble rise to different heights when...
Homework Statement
The question is to specify all forces and constraints that are applied in a system of a two-seat merry go round model in terms of the generalised coordinates - and their type (e.g. geometric, kinetic).
http://i.imgur.com/FQ7PJyg.png
The system is modeled as central...
Hi, I have been working on this problem for a while:
You place a book flat on a table and press down on it with your right hand. The hand-to-book and table-to-book coefficients of kinetic friction are 0.48 and 0.43 respectively. The book's mass is 1.14 kg and your downward push on it is 9.70 N...
Homework Statement
Lets say we have a series of balls and an eggs. All items have equal mass but are traveling at different velocities.
Thus they have differing kinetic energies.
Now, for each 'ball' object we have, we want to find an egg object with a similar kinetic energy. Let's say...
Homework Statement
Given a 2.0 kg mass at rest on a horizontal surface at point zero. For 30.0 m, a constant horizontal force of 6 N is applied to the mass.
For the first 15 m, the surface is frictionless. For the second 15 m, there is friction between the surface and the mass.
The 6 N force...
Homework Statement
The sports car ) is rounding a flat, unbanked curve with radius R . If the coefficient of static friction between tires and road is Us, what is the maximum speedat which the driver can take the curve without sliding?
why in this problem i am given Static fiction coefficient...
Homework Statement
A body is moving on a horizontal plane which gradually turns to another plane forming an angle ##α##. Friction coefficient is ##μ##. Find the kinetic energy of the body after the turn if in the beginning it was ##K_o##.
Homework Equations
Newton's laws.
The Attempt at a...
Homework Statement
Homework Equations
Please see below.
The Attempt at a Solution
I'm pretty sure my method is correct but I'm getting small answers:
$$
COM \\ \\
E_{6}= E_{2}+E_{\alpha}
\\
\\
Minus \ E_{2} \ and \ square \ both\ sides\\
\\
E_{6}^{2}+E_{2}^{2}-2E_{2}E_{6}=E_{\alpha}^{2}\\...
Homework Statement
Hi,I have been struggling on this problem for a whole day,looking for someone to sort it out!
My question:(please see the attached diagram as well)
Consider 2 spheres A and B,having different masses (m and M) but equal in size.
A is moving to the right at a speed u, B is...
I am trying to explain the convection heat transfer and the mass transfer related (buoyancy of the heated part of the gas) using only kinetic theory of gases , I mean using only collisions between molecules of the gas. The environment is the usual one : a hot wall in contact with a gas...
Homework Statement
So first the task:
Determine the average value of the kinetic energy of the particles of an ideal gas at 0.0 C and at 100 C (b) What is the kinetic energy per mole of an Ideal gas at these temperatures.
I took the above right out of the pdf we got from our professor.
I know...
good day all. I'm new in the area of bioremediation. Please is there any kinetic model relating bioremediation rate to temperature, depth, PH & Nutrient? if not, how can I model one? a simplified explanation,links & simple literature is also welcome. Many thanks
I am having trouble deciding when to use which equation.
If you're given the wavelength of a proton, let's say 100 fm, and have to find the kinetic energy of it, how would you do this?
Here are my ideas:
Idea 1: Use lambda = h/p, where p = sqrt(2Em).
Idea 2: Use E=(pc)^2+(mc^2)^2 =...
Homework Statement
Homework Equations
Q = c m ΔT
The Attempt at a Solution
so converting 55 mph to meters per sec gives me a velocity of 24.58 m/s
kinetic energy of car is 1/2 m v2
i set 1/2 m v2 = c m ΔT
plugging in v and c and masses of both
ΔT = 134.56
is that correct?
Homework Statement
A bullet of mass 2.0 * 10-3 kg is fired horizontally into a free-standing block of wood of mass 4.98 * 10-1 kg, which it knocks forward with an initial speed of 1.2 m s-1.
(a) Estimate the speed of the bullet.
(b) How much kinetic energy is lost in the impact?
(c) What...
Homework Statement
The problem is that my teacher asked to solve this using kinetic energy but i doubt it uses kinetic energy... i thought it uses potential energy.
[/B]
You put your little sister (mass m) on a swing whose chains have length L and pull slowly back until the swing makes an...
Homework Statement
The kinetic energy (in keV) of the alpha particle, when the nucleus 84210Po at rest undergoes alpha decay, is
A 5319
B 5422
C 5707
D 5818
Homework Equations
## E = mc^2 ##
Kinetic energy ## = mv^2/2 ##
The Attempt at a Solution
alpha particle is emission of helium nucleus...
Homework Statement
After being hit, a 0.145 kg baseball has a speed of 45.6 m/s.
1. What is the kinetic energy of the baseball after it has been hit?
2. How much work is done on the baseball by the baseball bat?
3. In moving through the air, the baseball slows down to a speed of 30.0 m/s...
As we know that every object that has kinetic energy could also have potential energy. Now suppose an object is in rest at a distance of h meter from ground so it has some potential energy and no kinetic energy, now if it starts to fall towards the ground can we say that its total potential...
I am curious about how a particle's kinetic energy changes with the explansion of the unverse. I calculated that for a matter dominated universe it would vary as 1/a2, while the photon temperature varies as 1/a. Is this correct? Is this also true in general? If so, the implication would be...
In case of quantum LHO in eigen state of the system ##|n \rangle##
\langle \hat{T} \rangle=\langle \hat{U} \rangle=\frac{1}{2}(n+\frac{1}{2})\hbar \omega
What will happened in some superposition of states? Does Ehrenfest theorem can tell me something more general? Is it possible to say that...
Homework Statement
Block M1 is on top of block M2 which is on top of a horizontal frictionless surface. A horizontal force, F, is applied to M1. The coefficient of static friction is us and the coefficient of kinetic friction isuk. Find, a) the maximum force that can be applied to M1, such...
I was wondering why the average kinetic energy is calculated in this manner.
They are dividing the kinetic energy function by the period (noted here as To) and integrating it with limits from 0→To. Why?
(This is a tiny portion of a larger textbook example, not an actual assignment.)
Sorry for...