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
How would the motion of the block look like when the Force of kinetic friciton is more than the Limiting value of static friction?
Homework Equations
Kinteic Friciton=μN
The Attempt at a Solution
I think the block after overcoming the limiting value of static friction will...
Hello,
A silly question I'm sure, if a projectile moving at 13.59 m/s with a KE = 527.47 J hits an area of 3 cm^2, what is the force transfer to that area and the resultant pressure applied expressed in Pascals?
Do I divide the KE by a volume instead of area to Pa?
Homework Statement
Show that $$L=\phi\Box^2\phi$$ generates negative energy density.
Homework EquationsThe Attempt at a Solution
The energy density is $$E=\frac{\partial L}{\partial \dot{\phi}}\dot{\phi}-L$$ Also the Lagrangian can be rewritten (using divergence theorem) as...
If i have two blocks on top of each other and there is friction between the two blocks and it's a kinetic friction ( given μk). if i was given the force applied on the lower block to the right direction for example. ignoring the friction between the lower block and the ground, i tried to draw...
The formula for kinetic energy is 0.5x kg x v^2, where v= velocity
The formula for joules is kg x v^2
I don't understand why does the difference exist
and what is the difference between joules and kinetic energy
isnt joule the unit for energy??
Thank you guys for helping me.
What happens to the kinetic energy when an object is disintegrated? Does it survive?
For example, if I throw a baseball at the sun at 100 mph, I will get X amounts of heat energy released and X amount of light as it burned up before contact. If I threw another baseball 100,000 mph into the sun...
Homework Statement
The problem is to Use the rest energy values in table 1 to calculate the maximum kinetic energy of the pions assuming the kaon is at rest before it decays.
Rest Energies of pions are π- 140, π0 135 and π+ 140.
Rest energies of kaons K- 494, K0 498 K+ 494
Homework...
Homework Statement
An object of mass 50 kg gains 20,000,000 joules every second. Devise formulae to find the distance covered at any given point in time, and the time necessary to cover a certain distance.
Homework EquationsThe Attempt at a Solution
E = 20,000,000 * t
V = (E * 2/50)1/2
That's...
Hello,
According to Special Relativity, the mass of an object must increase as its speed approaches the speed of light.
m=m0γ
In the formula that allows us to calculate the kinetic energy of a body, KE=0.5mv2, should we take into consideration such increase in mass?
Weam Abou Hamdan
Wednesday...
Homework Statement
Why is the value hf-w equal to maximum kinetic energy (not just kinetic energy) for a photoelectron?
2. The attempt at a solution
w is the energy needed for electron to escape the surface, so the rest should convert to KE, and no such need for defining KE(max) should be...
Hi guys, I need your support to formulate the kinetic energy of an object:
- having mass m [Kg]
- rotating with angular velocity o [rad/sec] referred to an axis t [m] distant (and parallel) to the symmetry axis of the object
- moving along the direction of its symmetry axis with a costant...
How do i suppose to determine the uncertainty for the slope of my Static friction against normal reaction graph?
My data for static friction and normal force has the uncertainty of +/- 0.0001
The uncertainty is too small for me to draw airbox/bar in the graph to draw the max and min slope...
Homework Statement
Mass m1 = 2kg traveling at v = 3 m/s
Mass m2 = 3kg traveling at v = 2 m/s
After an elastic collision (from opposite directions) what will be the momentum and velocities of each of the bodies ?
Homework Equations
[/B]
Momentum = mass x velocity
##K.E = \frac {1}{2}.m.v^2 ##...
Hi,
I was reading about magnetic reconnection in astrophysical plasma and it says that magnetic reconnection transforms magnetic energy into heat via ohmic dissipation, particle acceleration and kinetic energy.
It is not clear to me the difference between particle acceleration and kinetic...
If a celestial body's kinetic energy (say, the Moon's) surpassed the energy necessary to exceed the gravitational binding energy (GBE), would said body break apart because of it?
For example, the Moon is currently orbiting the Earth at a speed of 1020 meters per second, giving it a kinetic...
The average loss of energy in a material per unit length of a particle (in particular an electron, which is stable) is described by the quantity ##dE/dx##.
- for ionization it is given by the Bethe-Bloch formula $$-\left\langle {\frac {dE}{dx}}\right\rangle ={\frac {4\pi }{m_{e}c^{2}}}\cdot...
Homework Statement
Consider a point mass m attached to a string of slowly increasing length ##l(t)##. Them motion is confined to a plane. Find L and H. Is H conserved? Is H equal to the total energy? Is the total energy conserved? Assume ##|\dot{l}/l|<<\omega##
Homework EquationsThe Attempt at...
Do electromagnetic waves have potential and kinetic energy like springs, strings, etc. If so how are they calculated, inter-related? What is the total energy? Are the energies fluctuating over time?
I am a physics hobbyist so generally the first answers should come with the least mathematics...
As per work energy principle, the energy spent in moving an object is stored as kinetic energy.Flow work is done to make the fluid move.Why is it not included in kinetic energy (i.e) why kinetic energy and flow work are considered seperately?
Homework Statement
The speed of a 4.0-N hockey puck, sliding across a level ice surface, decreases at the rate of 0.61 m/s2. The coefficient of kinetic friction between the puck and ice is:
A) 0.062
B) 0.25
C) 0.41
D) 0.62
E) 1.2
Homework Equations
I'm not too sure but i know that :
If the...
Homework Statement
Light with a wavelength of 630nm is directed at a metallic surface that has a work function of 1.5 eV. Find:a) The maximum kinetic energy of the emitted electrons.
b) The cutoff potential required to stop the photoelectrons.
Homework Equations
Ek = hc / λ - W
Ek = eVo...
Help me please:)
(1) An idealized engine with constant torque curve means constant acceleration.
So for example if there is no air resistance and no frictions and car is on fixed gear and at 3000Rpm it produces 50Hp so at 6000Rpm will produce 100Hp.
So he doubles the speed , doubles power and...
Homework Statement
I'm trying to find the coefficient of restitution (COR) and energy loss upon impact of a bouncing ball, and I'm trying to understand how these relate to each other.
Homework Equations
COR=sqrt(2gh/2gH)
suvat equations (possibly)
1/2mv^2=mgH (using m=0.0585kg, g=9.8)
energy...
Homework Statement
Homework EquationsThe Attempt at a Solution
How to do part biii?
I tried to find change of U and W, then use ΔU-W=Q=0.
I can find the change in U by using the fact the rms of the x-component of the velocity is doubled. Therefore, originally, if isotropic <c2> =...
I'd like to know which methods I could use to reduce the loss of kinetic energy when two iron balls collide, or when a plastic ball collides with the floor after a free fall. I have tried to cover the floor with a fabric that would make it more elastic, but it had a small effect (if it hat...
Homework Statement
Let 3/2kT be the kinetic energy of ideal gas per molecules. T the absolute temperature and N the avogadro number. Answer the following questions :
1) when the volume doubled at constant temperature. How many times the kinetic energy per molecule become greater than before...
I hear somewhere explanation
why kinetic energy is proportional to $v^2$ and not to $v^3$, for instance.
https://www.physicsforums.com/threads/quadratic-forms-and-kinetic-energy.826884/
I wish to find reference for this.
Now I find your thread with the same question and very similar answers...
Homework Statement
https://www.physicsforums.com/attachments/upload_2018-4-29_12-40-30-png.224871/
Homework EquationsThe Attempt at a Solution
1/2mv^2=10
1/2m(ucos60)^2=10
1/2mu^2/4=10
mu^2=80
what to do now?
Information Given:Zero, a hypothetical planet, has a mass of 4.2 x 1023 kg, a radius of 2.8 x 106 m, and no atmosphere. A 10 kg space probe is to be launched vertically from its surface.
Question: (a) If the probe is launched with an initial kinetic energy of 5.0 x 107 J, what will be its...
Homework Statement
During the ##\alpha## decay of ##^{238}_{92}U## an ##\alpha## particle is fromed inside the nucleus. Given that the last 4 nucleons in ##^{238}_{92}U## have an average binding energy per nucleon of ##6.1MeV##, estimate the kinetic energy of the ##\alpha## particle when it is...
A steel washer is suspended inside an empty crate from a light string attached to the top of the crate. The crate slides down a long ramp that is inclined at an angle of 37 above the horizontal. The crate has mass 154 kg. You are sitting inside the crate; your mass is 61 kg. As the crate is...
The question is to find the change in kinetic energy of a system. the system in use is a pully system with a wooden block on a flat surface attached to a 100g mass. I have calculated force of friction between the block and desk, and using a ticker timer, I have individual speeds at every 0.1 of...
Homework Statement
I need to find the coefficient of kinetic friction from a set a lab data that I found. I had a mass connected to a mass hanger by a pulley, and measured the acceleration of the mass with various amounts of mass on the hanger. In the attached image, the acceleration was...
Homework Statement
Homework Equations
K = (1/2)mv2
U = mgh
W=Fd
Integration/Calculus
The Attempt at a Solution
I'm not sure what I should be doing for this question, if height changes how is it possible that velocity stays the same, according to the conservation of energy (frictionless wire)...
Homework Statement
a) Calculate the kinetic energy required to accelerate a single proton from a rest position to 0.9999c. The mass of a proton is 1.67*10^-27 kg.
b) Find the ratio of the kinetic energy to the energy of a proton at rest.
c) Explain why no particle accelerator will ever be able...
Homework Statement
A mass m is initially at rest. A constant force $F$ (directed to the right) acts
on it over a distance d. The increase in kinetic energy is therefore $Fd$.
Consider the situation from the point of view of someone moving to the left
at speed $V$ . Show explicitly that this...
Homework Statement
On a frictionless, horizontal air table, puck A (with mass 0.250 kg ) is moving toward puck B (with mass 0.360 kg ), that is initially at rest. After the collision, puck A has a velocity of 0.125 m/s to the left, and puck B has velocity 0.655 m/s to the right.
I already...
Homework Statement
[/B]
I have the following expression:
$$S=T+V$$
$$T=\frac{m}{\tau_0+it}((x_1-x_0)^2+(x_2-x_1)^2)+\frac{m}{2(\tau_1-it)}(x_2-x_0)^2$$
$$V= \frac{(\tau_0+it)}{2}(\frac{k_0 x_0}{2}+\frac{k_0 x_2}{2}+k_0 x_1)+(\tau_1-it)(\frac{k_1 x_0}{2}+\frac{k_1 x_2}{2})$$
The main goal...
Homework Statement
How much kinetic energy is in electron volts?
Homework Equations
Kinetic energy = 1/2 mv2
1 electron volt = 1.6 x 10-19 J
The Attempt at a Solution
[/B]
It's a bit unclear to me what the question is asking, since no context at all is given. It's one of the questions in...
Homework Statement
The question gave a force applied on a block as well as a distance. It also gave the work done by friction which was negative. The question was to find the change in kinetic energy.Homework Equations
Wnet = change in KE
The Attempt at a Solution
I found the work done by the...
Hi.
In all of my question, I mean degrees celsius when I say degree.
Think we have a 0 degree ice. we give some energy to it (by a heater) and all of it get into a 0 degree water.
How does the kinetic and potential energy of the molecules change?
In the book in which I saw this question, it...
Homework Statement
I am having trouble with Microsoft Excel formulas to obtain the correct data for Kinetic Energy 2 initial, KE1 final, KE2f, KEi, KEf, total KE and total KE%
Homework Equations
Microsoft office uses equations such as =(A2+B2) and I need to determine what is the appropriate...
Hi guys,
Yesterday I sat down, and just for fun, decided to calculate the coefficient of kinetic friction for the all electric Ford Focus. I keep getting the wrong answer, and it is driving me crazy. Here are the facts.
Battery: 23 kWh.
Curb weight: 1,651 kg.
Maximum travel distance before a...
Homework Statement
From a physics multiple choice test: "A car is raised to a height of 10 meters. The car is at rest both before and after it has been lifted. The mass of the car is 900 kg. The total work that has been done on the car during the move is"
(The right answer is: zero).
Wnet...
Homework Statement
B is 10kg
C is 20kg
can I find a lagrangian for this system? If so how?
Diagram: http://imgur.com/j811rzw
Homework Equations
L=T-V
Kinetic = .5mv^2
Potential = mgh
The Attempt at a Solution
I know the kinetic energy must be 0 right? How could I find the potential?
Hi everyone.
Given: an asteroid with the mass of 50,000,000 kg, which is moving with the velocity of oh-my-god particle -- 99.99999999999999999999951% of c.
Due to relativistic effects, its total kinetic energy will be 1.44 E+36 Joules (Lorentz factor = 3.2 E+11).
A hypothetical particle...
Homework Statement
Homework Equations
L = IW
RKE = .5IW^2
The Attempt at a Solution
Since the two solid spheres have equal radii and same angular momenta, except that the mass differs, i think that the inertia is equal. However, since sphere A is more heavy, it would spin slower than sphere...
Kinda looking to confirm what I already suspect.
All things being equal, if two objects have the same kinetic energy, does the fact that one is larger and heavier than the other (although at a slower velocity) mean anything?
Specifically when comparing bullets. One bullet .451" in diameter...
<< Mentor Note -- Two threads on the same subject have been merged >>
I am a junior enrolled in IB Physics at the standard level at my high school. As a part of the curriculum we must perform an Internal Assessment (IA) which involves performing an experiment and performing calculations and it...