Explore BrainMass


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

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

Charged particle fired at fixed charge

(See attached file for full problem description with proper symbols) --- A charge of -4.39 C is fixed in place. From a horizontal distance of 0.0132 m, a particle of mass 9.78 x 10-3 kg and charge -8.74 C is fired with an initial speed of 90.4 m/s directly toward the fixed charge. How far does the particle tr

Introduction to quantum mechanics past paper

2. Two possible wave functions for states of a particle, with definite energies E_1 and E_2 are: see attachement for equations. - Explain why these are called stationary states. - Write down a wavefunction for a non-stationary state for which the expectation value of the energy is (1/3*E_1) + 2/3*E_2). - Show that the p

Energy required to create a rabbit "out of thin air".

This figure indicates the energy required to conjure up the rabbit "out of thin-air". Evidently it takes more than energy, U=E, of the rabbit. Please explain, and also tell me why these energies are called "Free". In other words, why did scientists give them such a name? Which figure is correct or are they both correct ?

Non-Elastic Collision: Conservation of linear momentum

8. A 69.0 kg person running at an initial speed of v1 = 4.00 m/s jumps onto a m = 138 kg cart initially at rest. (Figure P8.47) The person slides on the cart's top surface and finally comes to rest relative to the cart. The coefficient of kinetic friction between the person and the cart is 0.400. Friction between the cart and g

Helium Electrons

The energy levels for the helium ion He^+ are given by a formula similar to that for the hydrogen atom: 9.7 x 10^-18/n^2 J and the radii of the stationary electron orbits are at r_n=2.65 x 10^-11 n^2 What is the difference between a He^+ ion and a helium atom? Calculate the radii of the n=2 and n=3 orbits of He^+ and show

Frequency of Motion

Solid, uniform cylinder of mass m and radius R is fitted with a frictionless axle along the cylinder's long axis. A horizontal spring (spring constant k) is attached to this axle. Under the influence of the spring, the cylinder rolls back and forth without slipping on a horizontal surface. What is the frequency of this motion?

Pulley Setup and Kinetic Energy

A m1 = 49.0 kg block and an m2 = 103.0 kg block are connected by a string as in Figure P7.28. The pulley is frictionless and of negligible mass. The coefficient of kinetic friction between the 49.0 kg block and incline is 0.250. Determine the change in the kinetic energy of the 49.0 kg block as it moves from A to B, a distance o

Solving for Height

An 11 kg bowling ball is dropped into a tub containing a mixture of ice and water. A short time later, when a new equilibrium has been established, there are 5.0 g less ice. From what height was the ball dropped? Part A Assume the bowling ball has an initial temperature of 0 degreesC, and that no water or ice splashes out.

Block Problems

1) A stationary block explodes into two pieces that slide along a frictionless floor and then into regions with friction, where they stop. The first piece, with a mass of 2.0 kg, encounters a coefficient of kinetic friction of 0.40 and slides to a stop in a distance 0.15 m. The second piece encounters a coefficient of kinetic fr

Photons of energy impinging upon helium ions

Photons of energy 65.561eV and 52.324eV impinge upon a collection of helium ions (He* , Z = 2). a. Can the photons of energy 65.561eV be absorbed by the helium ions without ejecting the electron from the ions if the electron is initially in the ground state? If so, to which state is the electron promoted? If not, why not?

Mechanics: Conservation of momentum, friction, kinetic energy and motion.

A 62.0 kg person running at an initial speed of v1 = 3.90 m/s jumps onto a m = 124 kg cart initially at rest. (Figure) The person slides on the cart's top surface and finally comes to rest relative to the cart. The coefficient of kinetic friction between the person and the cart is 0.350. Friction between the cart and ground can

Momentum and Collisions on a Frictionless Surface

Please help me with this question: On a frictionless horizontal air table, puck A (with mass .250 kg) is moving toward puck B (with mass .350 kg), which is initially at rest. After the collision, puck A has a velocity of .120 m/s to the left, and puck B has velocity .650 m/s to the right. a) What was the speed of puck A b

Rotational Motion: Rod released on smooth horizontal plane

A thin rod of length h and mass M is held vertically with its lower end resting on a frictionless horizontal surface. The rod is then released to fall freely. Determine the speed of its center of mass just before it hits the horizontal surface. Use h, M, and g for length, mass, and gravitational acceleration respectively. (b)

3 Physics Problems

(See attached files for full problem description with units and diagrams) --- A package of mass is released from rest at a warehouse loading dock and slides down a 3.0-m-high frictionless chute to a waiting truck. Unfortunately, the truck driver went on a break without having removed the previous package, of mass 2 , from

Motion in a vertical circle: conservation of energy

A pendulum consists of a string of length L and a bob of mass M. The string is brought to a horizontal position and given the minimum initial speed enabling a pendulum to make a full turn in the vertical plane. a) what is the maximum kinetic energy K of the bob? b) what is the tension in the string when the kinetic energy is

Find compression of spring at bottom of incline

A block of mass m starts from rest at a height h and slides down a frictionless plane inclined at theta with the horizontal. The block strikes a spring of force constant k. Find the compression of the spring when the block is momentarily at rest.

Calculating the Power of a Pump

Question: A pump is required to lift 800 kg of water (about 210 gallons) per minute from a well 14.0m deep and eject it with a speed of 18.0 m/s. a) How much work is done per minute in lifting the water? b) How much in giving the water the kinetic energy it has when ejected? c) What must be the power outpu

Collision in One Dimension

(See attached file for full problem description with diagrams and units) On a frictionless horizontal air table, puck A (with mass 0.369 ) is moving toward puck B (with mass 0.249 ), which is initially at rest. After the collision, puck A has velocity 0.116 to the left, and puck B has velocity 0.645 to the right. a)

Total Kinetic Energy difference to rotational kinetic energy

A thin stick of length L = 1.6 m is denser at one end than at the other: Its mass density is = (0.40 kg/m) - (0.03 kg/m^2)x, where x measures the distance from the heavier end of the stick. The stick rotates with period T = 1 s about an axis perpendicular to the stick through the heavy end. Determine the rotational kinetic ener

CN in molecular clouds

Cold, interstellar, molecular clouds have been seen to contain the cynogen molecule, CN, whose first rotational excited states have an energy of 4.7*10^-4 eV above the ground state. There are actually 3 such excited states, all with the same energy. In 1941, studies of these molecular clouds, using the absorption of starlight pa