Share
Explore BrainMass

Energy

Two problems on capacitors.

1. A controller on an electronic arcade game consists of a variable resistor connected across the plates of a 0.22 micro Farad capacitor. The capacitor is charged to 5.00V, then discharged through the resistor. The time for the potential difference across the plates to decrease to 0.800V is measured by a clock inside the game

Magnetic energy of solar flare

The problem reads as: "The magnetic field permeating a region of space represents stored energy. This energy is often quantified in terms of its density (magnetic energy per unit volume) given by B^2/(2*u) where u=4*pi X 10^(-7). Suppose an "X2" flare occurs within a volume of 10^12 km3 over a sunspot pair initially permeate

the kinetic energy of the electrons in the beam

A beam of electrons, each with the same kinetic energy, illuminates a pair of slits separated by a distance of 52 nm. The beam forms bright and dark fringes on a screen located a distance 2.3 m beyond the two slits. The arrangement is otherwise identical to that used in the optical two-slit interference experiment. The brigh

Charged spheres

1. A thin, spherical, conducting shell of radius R is mounted on an insulating support and charged to a potential of -125V. An electron is then fired directly toward the center of the shell, from point P at distance r from the center of the shell ( r>>R). What initial speed Vo is needed for the electron to just re

minimum surface charge density on the plate to stop protons

Protons exit a high speed proton machine at a speed of 1.50 * 10^6 m/s. A device needs to stop the protons safely. Protons will embed themselves in a metal target, but protons traveling faster than 1.30 * 10^5 m/s emit dangerous x rays when they hit. The protons must be slowed down to an acceptable speed, then let them hit a

A charged parallel plate capacitor with insertion of a dielectric slab.

A parallel plate capacitor with plate separation d is connected to a battery. The capacitor is fully charged to Q Coulombs and a voltage of V. (C is the capacitance and U is the stored energy.) Answer the following questions regarding the capacitor charged by a battery. For each statement below, select True or False. 1. Aft

Special Relativity - Energy Problems

A particle of mass 3.5 MeV/c2 and kinetic energy 4.5 MeV collides with a stationary particle of mass 0.5 MeV/c2 . After the collision, the particles stick together. (part 1 of 5) Find the total energy of the first particle before the collision. Answer in units of MeV. (part 2 of 5) Find the speed of the first particl

Loop the loop speed

See attached file for full problem description. A small object, released from a height of 15m slides along the frictionless loop-the-loop with a diameter of 4.3m. What is its speed at the top of the loop?

Measuring the speed of a bullet

You need to verify which gun fired a bullet in a police investigation with a very limited budget. There are two guns involved in a crime; both could fire bullets of the same kind of mass (0.1kg). One is an assault rifle which fires the bullet at speed of 300m/s; the other is a hand gun which fires the same bullet with speed of 2

emissivity and radiation

A.) The filament of a light bulb has a temperature of 3.1 103 °C and radiates 70 watts of power. The emissivity of the filament is 0.38. Find the surface area of the filament. B.) A car parked in the sun absorbs energy at a rate of 550 watts per square meter of surface area. The car reaches a temperature at which it radiat

Heat intensity

A dish of lasagna is being heated in a microwave oven. The effective area of the lasagna that is exposed to the microwaves is 1.6 10-2 m2. The mass of the lasagna is 0.26 kg, and its specific heat capacity is 3400 J/(kg°C). The temperature rises by 80.0°C in 7.0 minutes. What is the intensity of the microwaves in the oven?

Possibility of Perpetual Motion Machine

Physicists say that it is impossible to create a perpetual motion machine, a machine whose own activity keeps it running perpetually. What energy principle precludes the possibility of a perpetual motion machine?

Water skiing: determining height

A water skier lets go of the tow rope upon leaving the end of a jump ramp at a speed of 16.4 m/s. As the drawing indicates, the skier has a speed of 13.0 m/s at the highest point of the jump. Ignoring air resistance, determine the skier's height H above the top of the ramp at the highest point.

Relativistic Electric Potential Difference

For this question you need to know that an electron accelerated through an electric potential difference of V volts acquires a kinetic energy of V eV. (This question is best done by not converting to joules, but by exploiting the fact that mec2 is given as 0.511 MeV). i) What is v/c for an electron? a) Striking the screen

A Parallel Plate Air Capacitor

The plates of a parallel plate air capacitor are 1.2 nm apart and area of each plate is 20 x 10^-4 m^2. Find the capacitance. It is connected to a 40 V battery. (i) What is the charge on each plate? (ii) What is the energy stored in the capacitor? Repeat the calculations for the same capacitor with the air gap re

Determine the Speed of the Gear Rack

The gear rack has a mass of 6 kg, and the gears each have a mass of 4 kg and a radius of gyration k = 30 mm at their centers. If the rack is originally moving downward at 2 m/s, when s = 0, determine the speed of the rack when s = 600 mm. The gears are free to turn about their centers, A and B. (See attached file for fig. and

A .15kg block of ice is placed on a horizontal table. It is pushed back compressing a spring .045m, and the spring's constant is 1900N/m. The spring's mass is negligible. The tabletop is 1.2m above the floor. When the spring is released, the block slides off the table and onto the floor. With negligible friction between the block and the table, what is the speed of the block when it hits the floor?

A .15kg block of ice is placed on a horizontal table. It is pushed back compressing a spring .045m, and the spring's constant is 1900N/m. The spring's mass is negligible. The tabletop is 1.2m above the floor. When the spring is released, the block slides off the table and onto the floor. With negligible friction between the

Electrostatic Energy

A cylindrical capacitor consists of a long wire of radius R, and length L with a charge +Q and a concentric outer cylindrical shell of radius Rsub2, length L, and a charge -Q. (a) find the electric field and energy density at any point in space. b(b) how much energy resides in cylindrical shell between the conductors of radius

Electrostatic energy: Parallel Plate Capacitor

A parallel plate capacitor with a plate area of 2 m^2 and a separation of 1.0 mm is charge to 100 V. (a) What is the electric field between the plates? (b) What is the energy per unit volume in the space between the plates? (c) Find the total energy by multiplying your answer from Part (b) by the total volume between plates. (d)

Finding potential energy of conservative force

See attached file for full problem description. Previously it was considered a force of the form f = ixy + jcx^2 + kz^3, and found a value of "c" from the following list such that this was a conservative force. Note: there must really be extra 'constants' in front of each term, with magnitude 1 but the proper units (such as

Electric Energy Between Charged Spheres

Two hollow metal spheres are concentric with each other. The inner sphere has a radius of 0.1500 m and a potential of 85.0 V. The radius of the outer sphere is 0.1520 m and its potential is 82.0 V. If the region between the spheres is filled with Teflon, what is the electric energy contained in this space?

Rotational kinetic energy of a ball

A uniform ball with a mass of 125 g is rolling without slipping along the horizontal surface of a table with a speed of 4.50 m/s when it rolls off the edge and it falls towards the floor, 1.10 m below. What is the rotational kinetic energy of the ball just before it hits the floor? 0.506 J 0.732 J 1.05 J

Angular speed of a pencil

A pencil, 15.7 cm long, is released from a vertical position with the eraser end resting on a table. The eraser does not slip. Treat the pencil like a uniform rod. What is the angular speed of the pencil just before it hits the table? a) 13.7 rad/s b) 7.23 rad/s c) 24.5 rad/s d) 16.8 rad/s

Finding Electric Potential Difference

The potential at location A is 452 V. A positively charged particle is released there from rest and arrives at location B with a speed Vb. The potential at location C is 791 V, and when released from rest from this spot, the particle arrives at B with twice the speed it previously had, or 2vb. What is the potential at B?

Potential Energy Between Two Points

An electric force moves a charge of +1.80 x 10^-4 C from point A to point B and performs 5.80 x 10^-3 J of work on the charge. (a.) What is the difference (EPEa-EPEb) between the electric potential energies of the charge at the two points? (b.) What is the potential difference (Va-Vb) between the two points. (c.) Which point is

Determining Kinetic Energy: Example Problem

The moment of inertia of a uniform rod (about its center) is given by I = M/12. What is the kinetic energy of a 120-cm rod with a mass of 450 g rotating about its center at 3.60 rad/s? 0.350 J 4.20 J 0.700 J 2.10 J