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.
My mcat book says temperature is a measure of the total kinetic energy of a system. Then later on it says temperature is a measurement of the average kinetic energy of a system. Is this an error? Thank you.
Homework Statement
A 100 N force directed 37° below the horizontal is applied to a 30 kg object on a horizontal surface. If the magnitude of the acceleration of the object is 1.3 m/s2, what is the coefficient of kinetic friction (μk) between the object and the surface?
Homework Equations...
I read that based on temperature , electrons have kinetic energy in metals so they randomly move around the ion lattice.
when we apply current to a room temperature conductor, the electrons being charge carriers align and form current?
but what happens in the plates of a capacitor , when the...
Hi, all. Here is an expression about kinetic energy from analytical dynamics of Haim Baruh which confuses me.
"Consider a particle and the case which the kinetic energy is only quadratic in terms of velocity of the particle. We take the differential form of work-energy principle and remove...
So my professor said that the Kinetic energy of the particle in a 3D infinite well is dependent on position where in a 1D infinite well it's NOT dependent on position. She is sort of notorious for being wrong apparently and many of my undergrads are telling me she is wrong.
I understand that...
Hello folks! I have just come from a night at the pub with fellow students of life where over many a pint several mysteries of the universe were discussed. One of my friends asked me a question concerning special relativity that initially took me by surprise and which has me wondering about the...
This has been bugging me. Several respected propulsion scientists at the 2008 Joint Propulsion Conference claimed that interstellar travel within a human lifetime was impossible. The KE of a rocket traveling at a significant fraction of c would be enormous via KE=0.5 * m * v^2 and that...
Hi I need some help explaining kinetic moment and moment of the center of mass.
This is an example:
http://session.masteringengineering.com/problemAsset/1529176/3/Hibbler.ch17.p107.jpg
Okay I know that when you do moment equations:
The Moment forces about some point is = to the kinetic...
If thermodynamic temperature can be interpreted as the average kinetic energy in a system, is there a quantity defined as the standard deviation?
For example, let's say you poured some hot water into a cup of cold water. The instant you poured it the standard deviation of the system would be...
Homework Statement
A horizontal 845.0 N merry-go-round with
a radius of 4.3 m is started from rest by a
constant horizontal force of 74.0 N applied
tangentially to the merry-go-round. Find the
kinetic energy of the merry-go-round after
2.2 s. Assume it is a solid cylinder. The...
Homework Statement
A computer scientist has dropped a tiny pizza crumb onto a magnetic disk. Later, when it's turned on, the disk is rotating at 88 revolutions per second about its axis, which is vertical. The coefficients of kinetic and static friction between pizza crumbs and the disk are...
Linear Momentum question - help please
Homework Statement
A 15,000 kg loader traveling east at 20 km/h turns south and travels at 25 km/h. Calculate the change in the loader’s
kinetic energy.
linear momentum.
Homework Equations
KE2-KE1 = change in KE
p=mv
The Attempt at a Solution
a...
Homework Statement
Blocks A and B are moving toward each other. Block A has a mass of 2.0 kg and a velocity of 50 m/s, while B has a mass of 4.0 kg and a velocity of -25 m/s. They suffer a completely inelastic collision. The kinetic energy dissipated during the collision is:
Homework...
Homework Statement
At what energy does an electron become “relativistic”? Consider electrons with
kinetic energies of 50 eV, 50 keV, and 50 MeV. For each case, calculate the momentum
of the electron first using the non-relativistic formula for kinetic energy, and then using
the correct...
I read in a science magazine that you would be able to generate more energy by collecting a mass of water and tipping it through a turbine than from generating energy from the impact of that mass of water as individual raindrops. Now this may simply be to do with the technology we have that...
When does the Kinetic Work Energy Theorem not apply to a situation? Or better, is there a general form of the equation where work can equal the change in any energy? What is work besides a force and a distance?
Homework Statement
An ice block is being pushed through a displacement d→=(15m)i -(12m)j along an embankment with rushing water. It exerts F→=(210N)i -(150N)J on block. How much work on block does force do?
Homework Equations
W=Fxd
Pythogoreum equation
a^2 +b^2= c^2
The Attempt...
Homework Statement
A bullet of mass 4.2 g strikes a ballistic pendulum of mass 2.0 kg. The center of mass of the pendulum rises a vertical distance of 18 cm. Assuming that the bullet remains embedded in the pendulum, calculate the bullet's initial speed.
Homework Equations
The...
Hi all!
I have a problem on finding the first passage time for kinetic monte carlo model.
Suppose I have a linear kinetic model for n states:
S1<->S2<->S3<->...<->Sn
where all the rate constants k_ij for transition between any two states are known. Is there any general way to find out the...
Homework Statement
If the velocity of a rocket is 10 meters per second and its mass is 10 kg, its kinetic energy is:
a. 5000 joules
b. 500 joules
c. 10000 joules
d. 1000 joules
[b]2. Homework Equations [/b)
Ek= (1/2) mv2
The Attempt at a Solution
e=(.5)10x10(2)
E=5000 j
1. Homework Statement
What type of energy does a blackboard eraser have when I hold it steady three feet about the ground?
a. potential energy
b. kinetic energy
c. electrical energy
d. spring elastic energy
I think it is kinetic energy. But I am confused on the differences of...
If I needed to calculate the kinetic energy of a bar suspended by a rope at one of its ends, in other words, a bar pendulum, do I need to calculate the kinetic energy of the center of mass plus the kinetic energy relatively to the center of mass or do I need to calculate the kinetic energy of...
"A hockey puck is hit on a frozen lake and starts moving with a speed of 12 m/s. Exactly 5.0 s later, its speed is 6.0 m/s. What's the puck's average acceleration? What is the coefficient of kinetic friction between the puck and the ice?"
I've calculated the acceleration, but I'm stuck when it...
Homework Statement
A 100 kg refrigerator is on rest on the floor.How much work is needed to move the refrigerator at a constant speed for 6 m along with a floor friction force of 200 N ?
Homework Equations
I used ΔK = W(Fg)+ W (N) + W(f)+ W(T) =0
and W(Fg)+ W (N) = 0
so W(T)=-W(f)=f*...
Homework Statement
A 23.0 kg child plays on a swing having support ropes that are 2.10 m long. A friend pulls her back until the ropes are 41.0-degrees from the vertical and releases her from rest.
a.)What is the potential energy for the child just as she is released compared with the...
Homework Statement
I don't know how to solve this question.
28.8J of work were done in accelerating a mall of 1.8 kg from rest. Find its final velocity. I'm not sure which formula to use..Homework Equations
F=ma
W=Fs
KE=1/2 mv^2The Attempt at a Solution
I can't figure out which formula to use...
Homework Statement
A ring of mass Mb, radius b, is mounted to a smaller ring of mass Ma, radius a and with the same centre, and they are free to rotate about an axis which points through this centre and is perpendicular to the rings. Dust of mass Ms is distributed uniformly on the inner...
Homework Statement
With the work function of copper being 4.65eV calculate the kinetic energy of a photoelectron knocked out with a photon with wavelength of 200nm . Then calculate the velocity of the electron.Homework Equations
KE=hf-ø
The Attempt at a Solution
FIrst time I have done a...
Homework Statement
A 5kg ball (m), is to be dropped 1 meter (h) in a vacuum with no resistance in the Earth's gravity (g).
Use the speed and motion equations to show that its KE at impact is equivalent to its PE at its starting point.
Homework Equations
PE = mgh
KE= 1/2mv^2...
Hi everyone,
I have a question on the rate constant of a kinetic model(like the one we use in describing chemical reaction). Suppose we have the following model between two states A and B:
A--(a)-->B
A<--(b)--B
where a, b are the rate constant for the transition. So the corresponding...
If an electron is traveling at C/2, the Lorenz formula says that mass is about 1.15 me, do we get the value of KE simply multiplying 1/2mv2 by 1.15?
Is it as simple as that?
Homework Statement
a rocket explodes in flight into two equal mass pieces still going in the same direction with one piece moving twice as fast as the other. What is the ratio of the total kinetic energy of the pieces just after the explosion to that of the rocket just before?
Homework...
Homework Statement
Finding error in kinetic energyHomework Equations
K = \frac{1}{2} m v2The Attempt at a Solution
Measured mass and velocities have errors in them. So we have to use derivative method to calculate uncertainty in KE which is to find the square root of the derivatives of K...
A 10kg block is at rest on the floor, and then a force of 30 N pushes on the block horizontally. If the coefficient of static friction between the block and the floor is μs= 0.33 and the coefficient of kinetic friction between the block and the floor is μk= 0.20, what is the acceleration of the...
Homework Statement
A 5.0 kg box slides up a 10 m long frictionless incline at an angle of 20 degrees with the horizontal, pushed by a 40 N force parallel to the incline. What is the change in kinetic energy?
Homework Equations
Ek = 1/2 mv2
Ep = mghThe Attempt at a Solution
I tried to assume...
Homework Statement
At what rate does the solar wind carry kinetic energy away from the sun? Give your result first in watts, then as a fraction of the Sun's luminosity in photons, L=3.8*10^26 W
Homework Equations
KE=(1/2)mv^2
mass loss of sun- Msunloss=4πr2vρ
The Attempt at a...
A 4700 kg truck carrying a 900 kg crate is traveling at 25 m/s to the right along a straight, level road, as shown below.
Suppose the brakes are applied for 3.0s. During this 3.0s the truck travels 55 m.
1. Calculate the acceleration of the truck during the 3.0s interval. (Assume it is...
Homework Statement
Homework Equations
P = dW/dt
Change in work = Change in Kinetic Energy
The Attempt at a Solution
Since the integral of the power graph is work done in the system, and since it starts at 0, does this mean kinetic energy is the same thing? So I can probably make...
Hi
I don't understand why the relationship between kinetic energy and velocity is not linear. Consider the following situation:
1. A rocket is traveling through space at constant velocity with it's thrusters switched off.
2. The thrusters are fired at full blast for precisely one second...
Homework Statement
Question in entirety: Vladimir Putin has contacted you to redesign the ski jump at the Olympic games. In the ski jump, contestants begin at rest at the starting gate on top of a hill inclined at an angle of 30 with respect to horizontal. They then accelerate down the hill...
For a damped mechanical oscillator, the energy of the system is given by $$E = \frac{1}{2}m \dot{x}^2 + \frac{1}{2}k x^2$$ where ##k## is the spring constant. From there, I've seen it dictated that the average kinetic energy ##\langle T \rangle ## is half of the total energy of the system. This...
Homework Statement
During the ascent from a height R to a height 2R, the speed of the rocket changes
from 7600 m s–1 to 7320 m s–1. Show that, in SI units, the change ΔEK in the kinetic
energy of the rocket is given by the expression
ΔEk = (2.09 × 106)m.
m : mass of rocket
Homework Equations...
Homework Statement
Show that for a simple square lattice (in 2-D) with the lattice spacing = a, the kinetic energy of a free electron at a corner (point A in the figure below) of the first Brillouin zone is higher than that of an electron at the midpoint of a side of the zone (point B in the...
Hi,
I was wondering, how is it possible that different gases can have the same average kinetic energy?(at same temperature) Can anybody give me a SIMPLE explanation of this? Knowing that some particles will move faster than others, I wonder how this can be possible :/
It would really help ...
Two identical bottles contain the same number of molecules at ambiant conditions of temperature and pression.The first contains N2, and the second CO2.Tell if the it's true/false and explain why
The molecules of CO2 have more kinetic energy than the molecules of N2.
My answer : False...
Hi, I am currently in High School physics and we are going over Energy and Momentum. I have some questions about how and why they both work.
*all objects are assumed to have the same mass
Since [Kinetic Energy=1/2mv^2], an objects Kinetic energy is proportional to the square of its...
Homework Statement
The minimum wavelength observed in x-ray radiation is 1.23 angstroms. (1 angstrom = 10E-10m). What is the KE, in eV, of the primary electron hitting the target?
Homework Equations
eV = hc/λ
and since all the potential energy becomes kinetic...
is the answer simply...