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Electric potential energy

Does the electric field always move from positive to negative? If I'm told that a uniform electric field of magnitude 4.1 x 10^5 N/C points in the positive x direction, and a 4.5 micro-C charge moves 6.0 m in the positive x direction, and to find the electric potential energy (which is -11 J), does my equation look like this:

Electromagnatism Induction of a Metal Bar

A metal bar with length L, mass m, and resistance R is placed on frictionless, metal rails that are inclined at an angle (Data) above the horizontal. The rails have negligible resistance. A uniform magnetic field of magnitude B is directed downward. The bar is released from rest and slides down the rails. a) Is the direction

Equilibrium state of a mixture.

Question: Three liquids are at temperatures of 10 degrees C, 20 degrees C and 30 degrees C, respectively. Equal masses of the first two liquids are mixed, and the equilibrium temperature is 17 degrees C. Equal masses of the second and third are then mixed, and the equilibrium temperature is 28 degrees C. Find the equilibri

After a block and marble collide, the block executes SHM

A spring with negligible mass, and force constant k= 60 nt/m, has one end fixed, and the other end attached to a stationary block of mass M= 2.0 kg on a horizontal, frictionless table. At time t=0, a ball of mass m= .25 kg, with horizontal speed of Vb= 50 m/sec to the right before impact, hits the block and bounces off, then

Energy density in an electric field

A charge isolated metal sphere of diameter 10cm has a potential of 8000 V relative to V=0 at infinity. Calculate the energy density in the electric field near the surface of the sphere?

Energy Absorbance

A film badge worn by a radiologist indicates that she has received an absorbed dose of 2.3e-5 Gy. The mass of the radiologist is 67 kg. How much energy has she absorbed? Answer in mJ.

Answer in nm

A proton is located at a distance of 0.410 m from a point charge of +8.30 µC. The repulsive electric force moves the proton until it is at a distance of 1.56 m from the charge. Suppose that the electric potential energy lost by the system is carried off by a photon that is emitted during the process. What is its wavelength?

Atomic physics

Calculate the classical frequency for the light emitted by an atom. To do so, note that the frequency of revolution is v/2pir, where r is the Bohr radius. Show that as n approches infinity in f= 2pi2mk2e4/h3 times 2n-1/(n-a)2 n2 the expression varies as 1/n3 and reduces to the classical frequency.

Pogo Stick -- Kinetic Energy

Please see the attached file for full problem description. --- A child's pogo stick stores energy in a spring with a force constant of 2.50 x 10^4 N/m. At position A (XA= -0.100 m), the spring compression is a maximum and the child is momentarily at rest. At position B (Xb=0) the spring is relaxed and the child is moving u

Thermal Kinetic Energy Problem

As Fig. 8-44 shows, a 4.5 kg block is accelerated by a compressed spring whose spring constant is 640 N/m. After leaving the spring at the spring's relaxed length, the block travels over a horizontal surface, with a coefficient of kinetic friction of 0.25, for a distance of 5.9 m before stopping. (a) What is the increase in

Force Problem

The only force acting on a 2.4 kg body as it moves along the x axis varies as shown in Fig. 7-33 (attached). The velocity of the body at x = 0 is 4.0 m/s. (a) What is the kinetic energy of the body at x = 3.0 m? (b) At what value of x will the body have a kinetic energy of 8.0 J? (c) What is the maximum kinetic energy attai

Reading a Potiential Energy Curve

A single conservation force F(x) acts on a 1.0 kg particle that moves along an x-axis. The potential energy U(x) associated with F(x) is given by: U(x) = -4x e^(-x/4) J, where x is in meters. At x = 5.0m the particle has a kinetic energy of 2.0J. a) What is the mechanical energy of the system? b) Make a plot of U(x) as a

Energy and quantum level

What is the energy of the photon emitted when the electron of a hydrogen atom makes a transition from the quantum level n=3 to the level n=1?

Find the Lagrangian function

Find the Lagrangian function. Please see the attachment. The bottom part of the attachment that got cut off just says "of motion of the particle."

Lorentz Force: Desk-Top Sized Proton Accelerator

Your company is designing a desk-top sized proton accelerator, using a 500MN/C superconducting magnet to hold the protons in a circular path. Estimate the maximum kinetic energy that your accelerator can give protons. Express your answer in the conventional particle physics unit of electron-volts, where 1 eV=1.6*10^-19J. For

Conservation of Momentum and Energy,,

Problem: m1 starts from rest at height h. At the bottom of the frictionless slope stands mass m2. m1 is then let go, and collides with m2 an elastic collision. What will be the final height m1 will attain after recoiling from m2?

Springs and Forces

A child's toy consists of a piece of plastic attached to a spring. The spring is compressed against the floor a distance of 2.00 cm, and the toy is released. If the toy has a mass of 90 g and rises to a maximum height of 50.0 cm, estimate the force constant of the spring (in N/m). I need help on which equation/formula to use a

Spring action

"The launching mechanism of a toy gun consists of a spring of unknown spring constant. If the spring is compressed a distance of 0.139 m and the gun fired vertically, the gun can launch a 25.1g projectile from rest to a maximum height of 24.5 m above the starting point of the projectile. Neglecting all resistive forces, determin

KE, average speed

"A 48.5 kg student climbs a 5.90 m long rope and stops at the top. What must her average speed be in order to match the power output of a 140 W lightbulb?" Here's how I approached this problem: Since 1 W = 1 J/s, I set KE = 140 J. Then, v^2 = KE/((.5)m) = 140/24.25 = 5.77 Then v = 2.4 m/s But that's not the right an

The highest position the car reaches at the bottom of the hill

A 750 kilogram automobile is moving at 20.0 meters per second at a height of 5.0 meters above the bottom of the hill when it runs out of gasoline. The car coasts down the hill and then continues coasting up the other side unitl it comes to rest. Ignoring frictional forces and air resistance, what is the value of "h", the highes

Lifetime and energy uncertainty

The lifetime of a molecule in a certian electronic state is 10e-10 s. What is the uncertianty in energy of this state? Give the answer in J and in J/mol.

Speed of particle on an incline

A small particle slides along a frictionless wire. If the particle's speed at point A is 8.85m/sec how fast is it moving at point B if it must go up a 2m incline?