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 crate of bananas has an initial speed of 4.2 m/s2. It slides across a floor, traveling 6.0m before coming to a stop. Find the coefficient of kinetic friction between the crate and the floor.
Homework Equations
Fnet=ma
v2=v02+2aΔx
The Attempt at a Solution...
Hello everyone,
I am currently reading the pages from a book called Thermal Physics, which was written by Daniel Schroeder; the pages to which I refer are 10-13. In these pages, he derives the relationship \bar{T} = kT. Here is one line that intrigues me,
"So if this model is accurate...
Homework Statement
Two 0.3 Kg gliders collide elastically on a frictionless track. Prior to the collision , their total kinetic energy is 0.52 J and their total momentum is 0.12 Kg m/s [left] along the track. Calculate the final velocities of the gliders.
Homework Equations
m1vi1 + m2vi2...
Someone said the following and it just doesn't sit right with me. How do I effectively tell them what's wrong here?
"
It applies to physics the same, as can be seen with the Kinetic Energy Formula Ke = 1/2MV^2...
For instance in an elastic collision of two indivisible particles...
Why does m v^{2} stay constant? Why not m v^{3}?
[That is, where other type of energy are unavailable (potential, electrical, mass, etc.)]
In other words, why does the physical unit: kg \cdot m^{2} / s^{2} , or Joule...
This isn't homework. I'm reviewing physics after many years of neglect. As with most of my posts, I made this problem up.
Let object A have mass m_A and object B have mass m_B. One of A's surfaces is flat, as is one of B's. These flat surfaces are in contact and slide relative to each other...
http://en.wikipedia.org/wiki/Kinetic_theory#Pressure_and_kinetic_energy
Based on the derivation for P in the above link, one of the early steps was:
Δt = 2L/vx
which is fine since it is analyzing one specific wall of the container, but then in the next step:
F = Δp/Δt = mvx2/L
And...
Hi all,
I'm new here.
I am curious to know if I could simulate high velocity on an object by applying the forces (compression) to it that it would experience at those high velocities.
Also, I'm curious to know if this high velocity (Kinetic Energy) would generate heat, and if so, what's the...
Homework Statement
A trolley consists of an enclosed carriage of mass M supported by 4 wheels each of mass m/4. A simple pendulum consists of a bob of mass μ on a light rod of length l supported at a pivot attached to the roof; its motion is confined to a plane. a) Write down expressions for...
Homework Statement
*The experiments drawing is attached.
m=0.1kg
Ek at point O (the moment the ball is being pushed) = 1.25 J
D (0 ; 0) , C (0 ; 0.05), E (0.25 ; 0), F (0.50 ; 0), G (0.75 ; 0)
Friction is neglected
1.Complete the chart by typing if the value of each variable is rising /...
Homework Statement
could you help me for the question b?
Homework Equations
E = mc^2
The Attempt at a Solution
the mass of the alpha particle is 0.66466 x 10^-26 kg >> 4.022 u
put it into the equation, so
E = 4.022 x c x c = 3.615 x 10^17 eV >> 0.0579 joule
my answer is that, but my...
In my textbook, there is a problem that made me think a bit more (this is not what the textbook was asking).
In the problem, there is a 1500 kg car traveling at 30 m/s on a 10 degree sloped hill (the car is driving uphill). The driver slams on the brakes and skids to a halt. We have to...
Homework Statement
The electric field associated with a monochromatic beam becomes zero 1.2*10^15 times per second. Find the max kinetic energy of the photoelectrons when this light falls on a metal surface whose work function is 2.0 eV.
Homework Equations
The Attempt at a Solution...
Homework Statement
A 5.0 kg mass is released from rest, at the top of a frictionless 30° inclined plane. Calculate the kinetic energy of the mass when it has slid 40cm down the incline starting from rest. (ANS = 9.80 J)
Homework Equations
KE=1/2(mv^2)
a=v/t
d=v1t + 1/2a(t^2)
v2^2=v1^2...
I was trying to do some studying regarding the definitions of energy, and I've hit a road block.
I know that since velocity is frame-dependent, an object's kinetic energy as observed in two different frames will yield two different results. My initial expectation was that changes in...
Homework Statement
If the resultant force acting on a 2.0kg object is equal to (3i + 4j) N, what is the change in kinetic energy as the object moves from (7i -8j)m to (11i -5j)m
Homework Equations
w = Fd
Ek = 1/2mv2
The Attempt at a Solution
I assumed that Ek = w so I tried to...
Homework Statement
A sled of mass m is coasting on the icy surface of a frozen river. While it is passing under a bridge, a package of equal mass m is dropped straight down and lands on the sled (without causing any damage). The sled plus the added load then continue along the original line of...
Homework Statement A physics book weighing 20 N is dropped from a position 2.0 meters above the floor. a) what is the potential energy of the book before it is dropped? b) what is the kinetic energy of the book when it is 1.0 meter from the floor
Homework Equations Ek = 1/2mv^2 , Ep=...
Homework Statement
A 240g ball and a 570g ball are connected by a 48.0-cm-long massless, rigid rod. The structure rotates about its center of mass at 110 rpm.
Homework Equations
KE = Iω^2
I = 1/12(mr^2)
The Attempt at a Solution
Since it has two masses and two different radius...
Homework Statement
Hello,
I am a bit confused on when rotational kinetic energy exists and when linear kinetic energy exists. For example when we spin a string with a ball attached to the end it has kinetic energy of 0.5mv^2 of the ball when we were solving for velocity of the ball at certain...
Homework Statement
This time you construct a trebuchet. A counterweight (M = 550kg) is at one end a distance ℓ2 = 1.5m away from the pivot. The child (m = 10kg) is a distance ℓ1 = 3m away from the pivot. The mass of the uniform rod connecting the two is mrod = 35kg. When released from the...
Hey PF, this is just a quick question:
If there's a hoop of mass M and radius a rotating around its vertical axis (see pic) and I want to write the kinetic energy for the Lagrangian is it just T = \frac{1}{2} M a^2 w^2 ? Considering w the angular velocity
A boy sitting on a rotating chair (ignore friction) with his hands stretched outwards, pulls in his hands thus reducing the moment of inertia of the chair-boy system. The angular velocity will increase to conserve the angular momentum.
The kinetic energy of the system will also increase (as...
Hello everyone, I would appreciate some help with this problem:
The coefficient of kinetic friction between the 1.2 kg block in the figure below and the table is 0.38. What is the acceleration of the 1.2 kg block?
Homework Equations
F=M*A
Fk = μk * N
The Attempt at a Solution
I created...
Homework Statement
Given the following hypothetic wave function for a particle confined in a region -4≤X≤6:
ψ(x)= A(4+x) for -4≤x≤1
A(6-x) for 1≤x≤6
0 otherwise
Using the normalized wave function, calculate the...
Homework Statement
A solid cylinder is rolling along a horizontal plane and is friction less around its symmetric axis. The cylinder is pulled by a constant force, F and travels the distance, d. The cylinder does not glide and has a friction force, f on the ground.
Known values:
Mass: M...
Hi guys, I'm studying the Kinetic Theory of gases from Pauli's book Vol. 3. Here he describes a section on the Mean free path, where the probability of two particles with speed v and v' colliding is described as:What is f(v,v') here? Is it the velocity distribution function? If so, isn't it...
Homework Statement
Examkrackers Lecture question - MCAT Prep book
116. A student holds a beaker of pure liquid A in one hand and pure liquid B in the other. Liquid A has a higher boiling point than liquid B. When the student pours a small amount of liquid B into liquid A, the temperature of...
I am not following the template for the reason that this is a generic question.
Consider that the change in kinetic energy is 1J.
Suppose further you have two particles, both of equal mass that are gravitationally attracted to each other (and the change in energy comes from the fact that they...
Recently I have been troubled by several things which have been stated in my school physics classes, mainly concerning the classical kinetic energy formula and other formulae derived from it (as well as the 'Work Energy Theorem').
The classical formula for kinetic energy '(mv^2)/2' was first...
Hi there,
I always thought that kinetic energy was the energy associated to a movement, ie, I have a ball in movement so I had printed the energy of my body on it when I kicked the ball, right? So I gave energy to the ball that started to move it. energy -> movement.
However, I was reading...
Homework Statement
A 1.80m long pole is balanced vertically with its tip on the ground. It starts to fall and its lower end does not slip. What will be the speed of the upper end of the pole just before it hits the ground? [hint: Use conservation of energy]
l=1.890m
Homework...
Homework Statement
Consider the following statement: "The temperature of a gas is a measure of the speed of its particles (atoms and molecules). Now suppose that I mix two gases together, for example oxygen and carbon dioxide, which are initially at different temperatures; if I wait long...
Homework Statement
This is not a homework problem. Okay, it is -- but I have solved it correctly already, so the question is not there. I'm just not sure about a detail in one of many solutions.
We have a hollow cylinder with a uniform mass distribution rolling down an incline with some...
Homework Statement
A spherical object with moment of inertia 0.57mr2 rolls without slipping down an incline. At the bottom of the incline.
Homework Equations
For a sphere (or cylinder) rolling without slipping ω = v/r.
Rotational KE = ½Iω²
The translational kinetic energy = ½mv²...
I am wondering if this method is in use already somewhere, or if its possible to be used. For example, using the equation of gravitational potential energy a 100kg weight that freefalls 100 meters has 98,000 J of energy, which equals 24,000 watts after approx 4 seconds of freefall. Assuming I...
Homework Statement
b) During the operation of a machine, two shafts rotate in opposite directions and are then connected by a clutch system. Shaft 1 has a rotational speed of 800 rev/min, a mass of 35 kg and a radius of gyration of 375 mm. Shaft 2 has a rotational speed of 1100 rev/min, a...
Homework Statement
A 2.00-kg object traveling east at 20.0 m/s collides with a 3.00-kg object traveling west at 10.0 m/s. After the collision, the 2.00-kg object has a velocity 5.00 m/s to the west. How much kinetic energy was lost during the collision? (no image was given).
Homework...
Homework Statement
This question has two parts; the first part I understand but the second part I do not.
Part 1: What is the rotational energy of a planet about its spin axis? Model the planet as a uniform sphere of radius 6420 km, and mass 5.59x10^24 kg. Assume it has a rotational period...
Homework Statement
What is the minimum amount of kinetic energy of proton that hits another still proton so reaction ##p+p\rightarrow p+n+\pi ^+## is possible? How big part of the initial kinetic energy is used for kinetic energy of new particles?Homework Equations
The Attempt at a Solution...
Hi Everyone,
This is a real simple question, but I should make sure I have this right. In the following formula, is the value of P in watts?
P = 1/2 Aρv3
I'm assuming that this is in watts, but you know what they say about assuming. Thanks in advance for your help!
Cheers,
Rick
Homework Statement
What is the minimum amount of kinetic energy of electron that hits another electron, so ectra electron-positron pair is produced.
Homework Equations
##p^{\mu }=(E/c,\vec{p})##
The Attempt at a Solution
Before the collision:
##p^{\mu...
A 2-kg block is attached to a horizonal ideal spring with a spring constant of 200 N/m. When the spring has its equilibrium length the block is given a speed of 5 m/s. What is the maximum elongation of the spring?
Is not the solution simply:
1/2kx2 = 1/2mv2
x = (mv2/k)0.5
x = 0.5 m...
Homework Statement
A uniform solid sphere of mass M and radius R has a light, thin metal spike driven through it, so it is free to turn about this spike. So imagine a bowling ball on a stick that is free to rotate about this stick.
A bullet of mass m is fired at speed v into the ball at a...
Homework Statement
In a simple model of the wind speed associated with hurricane Emily, we assume there is calm eye 18.8 km in radius. The winds, which extend to a height of 4000 m, begin with a speed of 303.0 km/hr at the eye wall and decrease linearly with radial distance down to 0 km/hr at a...
A hollow, thin-walled sphere (ICM = 2MR2/3) of mass 20 kg is completely filled with a liquid of unknown mass. The sphere is released at the top of a plane inclined at 30° to the horizontal, and it rolls 20 m to the bottom in 3.6 s. What is the mass of the liquid?
2.My approach is...
Homework Statement
An 8-kg sphere A is moving to the left with a velocity of 15 m/s when it strikes the 45° inclined surface of a 10-kg block B which is moving to the right a 5 m/s. The ball strikes the block 1 meter above the ground. The block is supported by rollers and impact is perfectly...
What happens if a ball goes from rolling on a surface to a frictionless surface? I know friction is required for the ball to roll, so would the rotational energy be transformed into translational energy (the ball goes faster without rolling), or does something else happen?
Thanks!
Homework Statement
You are given Force as a function of distance (F vs x). Find the change in kinetic energy from $x=a $ to $x=b$.
Homework Equations
see attempt solution
conservation of energy equations
The Attempt at a Solution
Since F = -dU/dx we get the integral of F = U...