A sphere of matter, of mass M and radius a, has a concentric cavity of radius b. Find the gravitational force F exerted by the sphere on a particle of mass m, located a distance rfrom the center of the sphere, as a function of r in the range 0 ? r ? ? . Consider points r = 0; b; a and ? in particular.

A straight wire carries a 12-A current eastward and a second straight wire carries a 14-A current westward. The wires are separated by a distance of 42 cm. The force on a 6.4 m length of one of the wires is..

A uniform line charge of linear charge density = 2.9 nC/m extends from x = 0 to x = 5 m.

a) What is the total charge?

b) Find the electric field on the x axis at x = 6 m.

c)Find the electric field on the x axis at x = 11 m.

d)Find the electric field on the x axis at x = 250 m

e) Find the field at x = 250 m, using the approximation that the charge is a point charge at the origin.

f)Compare your result with that for the exact calculation in part (d).

A uniform disk of mass 371 kg and radius 0.19 m is mounted on frictionless bearings so it can rotate freely around a vertical axis through its center (see the following figure). A cord is wrapped around the rim of the disk and pulled with a force of 10 N. What is the angular velocity (in rad/s) at the instant the disk has completed four revolutions. The disk starts from rest.

Group of answer choices

3.78 rad/s

3.87 rad/s

2.35 rad/s

2.53 rad/s

Please state the mechanisms for generating (a) continuous wavelength and (b) characteristic wavelength X-rays in a X-ray tube. (c) explain the reason for the intensity of X-ray spectrum as changes with acceleration voltage of incident electrons to the metal target.

The figure shows an initially stationary block of mass m on a floor. A force of magnitude 0.500mg is then applied at upward angle θ = 20°. What is the magnitude of the acceleration of the block across the floor if (a) μ_s = 0.630 and μ_k = 0.530 and (b) μ_s = 0.430 and μ_k = 0.320?

The next two questions refer to the following physical situation:

Two blocks (masses m₁ = 30 kg and m₂ = 7 kg) sit atop one another as shown below. The coefficient of static friction between the blocks is μ_s= 0.32.  There is no friction between the lower block and the surface on which it rests. A constant external force F is applied to the lower block.

What is F_max, the maximum magnitude of this force such that the upper block does not slide with respect to the lower block?

If there is kinetic friction between the lower block and the surface, the magnitude of the maximum possible force F_max that can be exerted on the lower block before the upper block starts sliding with respect to the lower block...

A precocious child wants to determine the moment of inertia, I_o, of the local merry-go-round. The child measures the radius of the merry-go-round (R = 2 m), then weighs herself (m = 25 kg), then notices that when she moves from the center of the merry-go-round to the rim, the rotational velocity of the merry-go-round changes from 0.3 rev/sec to 0.2 rev/sec. If the child treats herself as a point mass, what moment of inertia does she estimate for the merry-go-round?

As the child moves from the center of the merry-go-round to the rim, the kinetic energy of the child plus the merry-go-round...

1. If a disk and a ring both have the same mass and radius, which one has the greater moment of inertia? Why is this so?
2. A figure skater doing pirouettes spins faster when she tucks her arms close to her chest and spins slower when she spreads out her arms. Explain this in terms of moment of inertia and Newton’s Second Law for rotational motion.

A cylindrical proportional tube has an anode wire radius of 0.003 cm and a cathode radius of 2.0 cm. It is operated with an applied voltage of 2000 V. If a minimum electric field of 1.0 MV/m is required to initiate gas multiplication, what fraction of the internal volume of the tube corresponds to the multiplication region?

A 0.92 kg mass is attached to a light spring with a force constant of 30.9 N/m and set into oscillation on a horizontal friction-less surface. If the spring is stretched 5.0 cm and released from rest, determine the following.

(a) maximum speed of the oscillating mass? in m/s ?

(b) speed of the oscillating mass when the spring is compressed 1.5 cm? in m/s ?

(c) speed of the oscillating mass as it passes the point 1.5 cm from the equilibrium position? in m/s ?

(d) value of x at which the speed of the oscillating mass is equal to one-half the maximum value? in m?

An apple falls from a tree and feels no air resistance. As it is falling, which of the following statement is correct?

After a trip to the store a 70.0-kg person is carrying heavy bags perpendicular to the direction of motion. How much work is being done by the person on the bags? Use the definition of work to show your result.

b) He takes a rest on a bench and leaves his bags on the ground. Sketch a free-body diagram for each of the three objects shown in the Figure.

c) Once he gets back to his apartment building he takes an elevator up. What acceleration of the elevator is necessary for his weight to increase by 10.0%?

Two converging lenses

(f₁ = 9.40 cm

and

f₂ = 5.50 cm)

are separated by 17.9 cm. The lens on the left has the longer focal length. An object stands 12.4 cm to the left of the left-hand lens in the combination. Locate the final image relative to the lens on the right. Obtain the overall magnification. Is the final image real or virtual? With respect to the original object, is the final image upright or inverted and is it larger or smaller?

(a) Locate the final image relative to the lens on the right.
cm  ---Select--- to the right of the right-hand lens to the left of the right-hand lens

(b) Obtain the overall magnification.


(c) Is the final image real or virtual?

realvirtual    

(d) Is the final image upright or inverted?

uprightinverted    

(e) Is it larger or smaller?

largersmaller   

(about solid state physics, optical communication)
The main principle of optical communication is the concept of total reflection. I wonder if the total reflection is based on particle property of light, or wave property of it.

The total reflection is the concept of refraction and reflection. I know that refraction and reflection of light are all properties that correspond to the particle and wave of light.(I mean, Particle property of light can explain refraction and reflection, and Wave property of light too.)
So.. Is it right if total reflection is using(based on) both particle and wave properties of light???