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# Energy

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### Two Pendulums

Two pendulums are hung adjacent to each other as shown in the picture. Bob #1 has a mass m, and bob #2 has a mass 2m. Bob #1 is pulled aside until the support string makes an angle of 45 degrees with the vertical direction and then released. When the bobs collide, they stick together. What is the maximum angle made by the suppor

### What is the ratio of the masses of the two marbles?

A child playing marbles shoots a marble directly at another marble at rest. The first marble stops, and the second marble continues in a straight line with the same speed that the first marble had initially. What is the ratio of the masses of the two marbles? I need to see each step and formula to solve this question.

### Motion of a freely falling body

An egg falls from a nest at a height of 3.08 meters. What speed will it have when it is 0.5 meters from the ground? Neglect air friction. I need to see each step and formula to solve this question.

### A block slides on a semicircular frictionless track.

A block slides on a semicircular frictionless track. If it starts from rest at position (A), what is its speed at the point marked (B)? A picture of the block and slide is attached as a jpeg file. I believe the answer is 3.7 m/s. I need to see each step and formula to solve this question.

### Value of the spring constant k

A 750-gram air-track glider slides along at a speed of 0.85 m/s until it hits a spring attached to the end of the very heavy track. The spring is compressed by 1.35 cm at the maximum compression. What is the value of the spring constant k? I need to see each step and formula to solve this question.

### Potential Energy Example Questions

A 0.302-kg coffee mug rests on a table top 0.740 meters above the floor. A) What is the potential energy of the mug with respect to the floor? B) What is the potential energy with respect to the counter top 1.100 meters above the floor? I need to see each step and formula to solve this question.

### Ratio of Kinetic Energies

Sam can throw a baseball twice as fast as can his little brother, Bill. How many time as much kinetic energy can Sam give the baseball as Bill can?

### Energy in the motion of a Ping Pong ball and maximum speed

A 2.5-g Ping-Pong ball at rest is set in motion by the use of 1.8 J of energy. If all of the energy goes into the motion of the ball, what is the balls maximum speed? I believe the answer is 38 m/s. I need to see each step and formula to solve this question.

### Rotational and Linear Speed & Kinetic Energy

A full keg of beer weighs 170 lbf. The beer inside the keg weighs 124lbf and the container weighs 46lbf. The keg is placed at the top of ramp length L=8ft. from the back of your pickup truck to the ground and released. Find: 1. The rotational and linear speed of the keg at the bottom of the ramp. 2. The kinetic engery of th

### Illuminance and intensity of light.

1). According to its package, a 100 watt light bulb emits 1140 lumens. For simplicity, assume the bulb provides isotropic illumination and ALL its emission is at 555 nm. A video camera is advertised as having "0.2 lux sensitivity", meaning it can record objects which receive at least this illuminance. In a dark room with no

### Window Energy Transfer

A window has a glass surface area of 1.6x10^3 cm^2 and a thickness of 3.0 mm. a) Find the rate of energy transfer by conduction through the windows when the temperature of the inside surface of the glass is 70 degrees F and the outside temperature is 90 degrees F. b) Repeat for the same inside temperature and an outside t

### 1D motion of a quantum particle

Consider the 1D motion of a quantum particle in an external potential with its total energy given by the equation in the attachment. (a) Explain why according to quantum mechanics, the ground state energy (i.e. the lowest possible energy of the particle) can never be zero. (b) By making use of a certain fundamental particl

### Peak Electric Field in the Wave

A point source emits light energy uniformly in all directions at an average rate Po with a a single frequency f. Show that the peak electric field in the wave is given by: Eo = (µocPo/2 r2) (Everything is under the square root) I think we have to prove that the peak electric field is that equation but once again I am lost

### Physics: Path Integrals, Navier Stokes, Cartesian Coordinates

(See attached file for full problem description) I am not sure how to solve these. Questions involves calculating path integrals, Navier Stokes equation, Cartesian coordinates, and conservation laws. Examples similar to these would be very helpful.

### Particle in a potential well

A particle of mass m moves in the potential V(x) = -g*delta(x) x>-a infinity x<-a (delta (x) = dirac delta function) a. Without worrying about continuity or boundary conditions, write down the general solution of the Schrodinger equation for a bound state (energy E<0) in regions( -a less than x les

### Relativity: Pulse rate of Earth observer for astronaut traveling in space; Determine the energy required to accelerate an electron between speeds

1.) An astronaut is traveling in a space vehicle that has a speed of 0.510c relative to Earth. The astronaut measures his pulse rate at 73.0 per minute. Signals generated by the astronaut's pulse are radioed to Earth when the vehicle is moving perpendicularly to a line that connects the vehicle with an Earth observer. What pu

### Wavelength and Zeeman Lines

What is the wave length of those three kinds of Zeeman lines emitted when the electron had occurred the transition from 3d(n=3, l=2) to 2p(n=2, l=1) about the hydrogen atom in the magnetic field of 10,000 gauss. *In the 3d(n=3, l=2) to 2p(n=2, l=1), l means lowercase of L.

### Oscillations: The spring with varying force constant

Please see attachment. Thanks. --- Many real springs are more easily stretched than compressed. We can represent this by using different spring constants for and for . As an example, consider a spring that exerts the following restoring force: A mass on a frictionless, horizontal surface is attached to this spring,

### Calculate the upward force on the airplane wings given the air speed above and below the wings and wings area.

What is the net upward force on an airplane wing of area 17.9 m^2 if the speed of air flow is 295 m/s across the top of the wing and 280 m/s across the bottom.

### Force of Friction and Gravitation Potential Energy

An electric winch pulls a 30.9 kg case of soap up a roller incline 3.01 m high in 3.15 seconds. The case starts from rest at the bottom and is moving 4.02 m/s at the top of the incline. The force of friction on the box is 39.4 N. a) What is the increase in gravitational potential energy of the box? b) Calculate the length

### Angular Speed of Rotating Hoop

A string is wrapped several times around the rim of a small hoop with radius r and mass m . The free end of the string is held in place and the hoop is released from rest. Calculate the angular speed of the rotating hoop after it has descended a distance, h. (See attached file for diagram and figures)

### Momentum & Collisions (Rifle Bullet)

A rifle bullet with mass 8.00 g strikes and embeds itself in a block with mass 0.992 kg that rests on a friction-less horizontal surface and is attached to a coil spring. The impact compresses the spring 15.0 cm. Calibration of the spring shows that a force of 0.750 N is requires to compress the spring 0.250 cm. 1. Find the

### Springs and Inclined Planes

1. A light horizontal spring has a force constant of k=100 N/m. A 2.00 kg block is pressed against one end of the spring, compressing it 0.100 m. When the block is released from rest it moves 0.250 m to the right of release position. Show that the coefficient of kinetic friction between the block and the horizontal surface is

### Mechanical Energy: Block Projected up the Incline by Spring

A block with mass m = 2.00 kg is placed against a spring on a frictionless incline with angle = 30.0° (Figure 8-43). (The block is not attached to the spring.) The spring, with spring constant k = 19.9 N/cm, is compressed 24.0 cm and then released. How Far along the incline is the highest point from the release point? I

### Potential Energy and Energy Conservation

A hydroelectric dam holds back a lake of surface area that has vertical sides below the water level. The water level in the lake is a height above the base of the dam. When the water passes through turbines at the base of the dam, its mechanical energy is converted into electrical energy with n efficiency. 1. If gravitationa

### DC Circuits: Energy and Current

Assume that the length of an axon membrane of about 10 cm is excited by an action potential (length excited = nerve speed x pulse duration = 50 m/s x 2.0 ms = 10 cm). In the resting state, the outer surface of the axon wall is charged positively with K+ ions and the inner wall has an equal and opposite charge of negative org

### Work and Kinetic Energy

The spring of a spring gun has force constant k = 400 N/m and negligible mass. The spring is compressed 6.00 cm and a ball with mass 0.0300 kg is placed in the horizontal barrel against the compressed spring. The spring is then released, and the ball is propelled out the barrel of the gun. The barrel is 6.00 cm long, so the ball

### Kinetic Energy of a rotating bar

A thin, uniform 12.0-kg bar that is 2.00 m long rotates uniformly about a pivot at one end, making 5.00 complete revolutions every 3.00 seconds. What is the kinetic energy of this bar? (Hint: Different points in the bar have different speeds. Break the bar up into infinitesimal segments of mass dm and integrate to add up the

### Energy Stored in Capacitor

Consider a parallel plate capacitor with area A and separation d. The plates have fixed charges Q and -Q, and no battery connected. Determine the energy stored before and after the insertion of a dielectric with dielectric constant K that completely fills the space between the plates.

### Parallel plate capacitor: Find the energy stored

1. Consider a parallel plate capacitor, fixed area A, and fixed separation, d. Find the energy stored, and after insertion of a slab of dielectric, which completely fills the space between the plates for each of the two cases (a) The plates are connected to a battery which maintains constant potential difference (b) The pl