Kinetic energy Definition and 1000 Threads

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...

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...

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...

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...

Classical physics

Homework Statement While playing around with basic QM, I tried using the hamilton operator to find the kinetic energy of a hydrogen atom in its ground state. I assume the wave function ##\psi_1## is known. However, I of course ran into problems... 1) in my solution attempt below, I end up with...

A mass moves through space-time at constant velocity. Space-time around this mass is warped by the mass and as the mass moves through space-time it causes unwarped space-time to warp and already warped space-time to warp more. In addition, the space-time it has moved through de-warps. Why...

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...

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 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...

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...

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...

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 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...

So today in class we were talking about gravity and my professor said that generally KE = -.5PE And so TME = .5PE I don't understand how that works.

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...