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# Work

### Energy Stored in a Spring

The force exerted by an unusual spring when it is compressed a distance x from equilibrium is given by F = -kx-cx^3, where k=220 N/m and c=3.6 N/m^3. Find the energy stored in this spring when it has been compressed by 15 cm.

### Work done by the force

A 5.0 kg object moving on a horizontal surface has an initial velocity, vi=(5.0i+10.0j) when a force F acts on the object for 3 seconds after which velocity is vf=(10i+30j) m/s. Determine the work done by the force F on the object. What is the magnitude of the force F?

### conservative force and the corresponding potential energy

Which of the following forces is conservative? (a)F=k(x,2y,3z) where k is a constant. (b)F=k(y,x,0)(c)F=k(-y,x,0). For those which are conservative, find the corresponding potential energy U, and verify by direct differentiation that F=-gadU.

### angular velocity of the particle and work done

A particle of mass m is moving on a frictionless horizontal table and is attached to a massless string, whose other end passes through a hole in the table, where I'm holding it. Initially, the particle is moving in a circle of radius r0 with angular velocity w0, but I now pull the string down through the whole until at length r

### electron and the infinite charged plane

An electron is released from rest 2.0 cm from an infinite charged plane. It accelerates toward the plane and collides with a speed of 1.0 x 10^7 m/s A) What is the surface charge density of the plane in C/m^2? B) What is the time required for the electron to travel the 2.0 cm?

### Two problems on electric potential

Please refer attachments.

### Heat Engine Operating Between A Water Tank and A River

A heat engine operates between a tank containing 1*10^3 m^3 of water and a river at a constant temperature of 10 degrees Celsius. If the temperature of the tank is initially 100 degrees Celsius, what is the maximum amount of work that the heat engine can perform?

### Physics

A disk with rotational inertia of 5.0 kg*m^2 and radius of 0.25m rotates on a fixed perpendicular axis through its center. A force of 2N is applied tangentially to the rim. As the disk turns through half a revolution what is the work done by the force?

### work done by each force on a box being pushed

A 48 kg box is being pushed a distance of 7.0 m across the floor by a force P whose magnitude is 143 N. The force P is parallel to the displacement of the box. The coefficient of kinetic friction is 0.25. Determine the work done on the box by each of the four forces that act on the box. Be sure to include the proper plus or minu

### change in electric potential energy

1. A uniform electric field with a magnitude of 6050 N/C points in the positive x direction. Find the change in electric potential energy with a +12.5-µC charge is moved 5.50 cm in (a) the positive x direction (b) the negative x direction, and (c) in the positive y direction. 2. Points A and B have electric potentials of

### Work done in reducing the distance between two charges

Two positive charges of +0.2 µC and +0.01 µC are placed 10 cm apart. Calculate the work done in reducing their distance to 5 cm.

### How do lasers work?

Describe how a thorough understanding of the energy levels in atoms was necessary before lasers could be developed.

### Change to Rotation Period with Tripled Radial Acceleration

On your first day at work for an appliance manufacturer, you are told to figure out what to do to the period of rotation during a washer spin cycle to triple the radial acceleration. What do you tell her?

### how far does the box slide before it stops

Box slides with v=4.5m/s down a horizontal surface. At point P, it encounters a rough section. The coefficient of friction is not constant. It begins at .100 at P and increases linearly to .600 at a distance of 12.5m away from P. A) Using work-energy theorem, how far does the box slide before it stops? B) What is the coef

### Determine how far the skier will slide before coming to rest

A skier on a slope inclined at 4.7 degrees to the horizontal pushes on ski poles and starts down the slope. The initial speed is 2.7m/s. The coefficient of kinetic friction between skis and snow is .11. Determine how far the skier will slide before coming to rest.

### Calculate the tension of the string in Newtons.

The goal is to give a guitar maker a list of the separation between successive frets on the neck of the guitar. In the figure attached, the frets are the thin metal bars transverse to the neck of the instrument. When a string is pressed against a fret with a finger, its effective length is the distance from the fret to the bridg

### Frictional force doing negative work

Give an example of a frictional force doing negative work. Explain how the friction does work in detail.

### Gravitational force as object moves up inclined plane

What is the amount of work done by the gravitational force as an object with a mass of 2.00 kg moves up an inclined plane that rises at an angle of elevation of 30 degrees? The question refers to the instant when the object has moved 0.600 m along the surface of the inclined plane in the upward direction. Neglect friction and

### A 100 kg object is pulled vertically upwards by a constant

A 100 kg object is pulled vertically upwards by a constant force of 4000 N for a distance of 20.0 m. What is the work done by the applied force on the object? 60,400 kg m/s 80,000 kg m/s 80,000 kg m^2/s^2 60,400 kg m^2/s^2

### Probability of energy flowing into a subsystem

Suppose we have two blocks composed of 6 harmonic oscillators each and have 3 quanta in each initially. After bringing them together, what is the probability of having all the energy move to one of the blocks?

### work done to pull the rope on the bench

Please see attached file for specifics. 1. A rope having a total mass of 0.4 kg and total length of 4.0 meters, has 0.6 m of the rope hanging vertically down off a work bench. How much work must done to place all the rope on the bench?

### When 2 objects w/ a difference in time will become equal

A television is dropped from the top of a cliff, and 1 second later a second television is thrown downward with a velocity of 20 m/s. How far below the cliff will the second television overtake the first? Could you please show me the detailed work (with the equations) of how to achieve the answer. Our teacher gave us the an

### Modern Physics Multiple Choice Questions

1. Use the work-energy theorem to find the force required to accelerate an electron (m = 9.11 x 10-31 kg) from rest to a speed of 1.50 x 107 m/s in a distance of 0.0125 m. a. 8.20 x 10-15 N b. 5.47 x 10-22 N c. 8.20 x 10-17 N d. 1.64 x 10-14 N e. 3.56 x 10-19 N 2. Use the work-energy theorem to find the force requir

### Calculating the Stopping Distance of a Car

A car is traveling on a level road with speed v_o at the instant when the brakes lock (preventing tire rotation) so that the tires slide rather than roll. Questions: A. Use the work-energy theorem to calculate the minimum stopping distance of the car in terms of v_o, g, and the coefficient of kinetic friction, mu_k between

### Life versus Intelligent Life

1. Contrast life to intelligent life? 2. Would it be possible to receive and understand a message from an extraterrestrial intelligent civilization.

### work done by the piston to increase the nitrogen volume

A piston assembly changes the volume of 5 grams of nitrogen from Vi=0.03 cubic meters to Vf=0.75 cubic meters isothermally at room temperature. What is the amount of work performed by the piston? I know that nitrogen is a diatomic molecule.

### Projectile Motion: Conservation of Energy

Discuss projectile motion - an easy approach.

### motion of a crate

Find the Following: A. What is the kinetic energy of the crate as it slides on the upper surface? B. While the crate slides along the upper surface, how much gravitational potential energy does it have compared to what it would have on the lower surface? C. What is the speed of the crate when it arrives at the lower sur

### Kinetic frictional force

A 1.00 x 10^2 kg crate is being pushed across a horizontal floor by a force P that makes an angle of 30.0 degrees below the horizontal. The coefficient of kinetic friction is 0.200. What should be the magnitude of P, so that the net work done by it and the kinetic frictional force is zero?

### Riemann tensor for the metric ds^2 = c^2dt^2 - dx^2 - a(t)^2 dy^2

1. Suppose we have a 2+1 dimensional spacetime described by the line element ds^2 = c^2dt^2 - dx^2 - a(t)^2 dy^2 where a(t) is an increasing function of time. (a) How do you interpret the spatial part of this geometry? In other words, can you describe its shape? (b) Calculate (by hand) the nonzero components of the cur