3 boxes, having masses m1=5kg, m2=10kg and m3=15 kg are stacked "sideways" (i.e., in x-) on a surface with coefficient of kinetic friction 0.7 mu_k; an external force of magnitude 15 N pushes on the right-most box, making an angle of 30 degrees relative to the horizontal; a second force of magnitude 20 N pushes in the opposite direction on the left-most box, as a result of which all three accelerate uniformly. Determine the numerical value all of the forces acting on each of the boxes (including all normal forces between the boxes), as well as the amount the boxes have moved after a time of 7 seconds. Keep in mind that the normal force acting specifically on the box subject to the external force is changed by the external force...

please make a diagram

Please Show work

1) A certain medical machine emits x-rays with a minimum wavelength of 0.025 nm. One day, the machine has an electrical problem and the voltage applied to the x-ray tube decreases to 74% of its normal value. Now what is the minimum x-ray wavelength produced by the machine?

?min = _________ nm

2) What is the maximum x-ray energy this machine (with electrical problems) can produce?

Emax = _________ eV

3) The atomic number of an element is 82. According to the Bohr model, what is the energy of a K? x-ray photon?

E = ___________ eV

A yo-yo has a rotational inertia of 900 g · cm2 and a mass of 100 g. Its axle radius is 3.2 mm, and its string is 120 cm long. The yo-yo rolls from rest down to the end of the string. (a) What is the magnitude of its linear acceleration? (b) How long does it take to reach the end of the string? As it reaches the end of the string, what are its (c) linear speed, (d) translational kinetic energy, (e) rotational kinetic energy, and (f) angular speed?

1. Water is in the big beaker in the figure on the left. Scale 1 reads 58 newtons, scale 2 reads 908 newtons, and scale 3 reads 0 newtons. The hanging block has a density of 10

1. Four masses of values 3, 7, 2 and 5Kg lie at the corners of a rectangle of dimensions 8 by 7 m (x by y). Placing the 3kg mass at the origin and the 7Kg mass along the x-axis and the 2 kg mass on the y-axis and the 5kg mass at the point (8,7), where is the center of mass of the system.

How would you connect a pair of equal resistors across a battery in order to get the most power dissipation in the resistors?

From a point 96 ft above the ground, a stone is thrown in such a way that it is at the same point: 3 sec after it was thrown, as it was 2 sec after it was thrown. How long does it take the stone to reach the ground?

The minimum stopping distance for a car depends on the driver’s reaction time and the car’s acceleration when the brakes are applied. A 1000 kg car traveling on a level road at speed 18 m/s travels 15 m (due to driver’s reaction time) before braking starts and then skids with the wheels locked another 30 m. Answer the following questions concerning this stopping process. (Ignore air resistance and assume g = 10 m/s^2.)

a) What is the driver’s reaction time?

b)  How long did it take for the car to come to a complete stop: include both segments – the one when the car was still going at a constant speed, and the other one when the car brakes were applied?

c) Sketch a v(t) (I believe it is a velocity-time) graph for the car motion for the entire braking process of the car: from the moment the driver noticed danger to the moment the car completely stopped. Indicate relevant times and velocities on the graph.

d) Show that the magnitude of the net force acting on the car when the car was skidding was 5400 N.

I'm not sure how I should start this. If someone could explain and answer It would be great. (:

1. If 55.1 cm of copper wire (diameter = 1.18 mm, resistivity = 1.69 × 10^-8Ω·m) is formed into a circular loop and placed perpendicular to a uniform magnetic field that is increasing at the constant rate of 12.6 mT/s, at what rate is thermal energy generated in the loop?

2. A rectangular loop (area = 2.7 m²) turns in a uniform magnetic field, B = 3.2 T. When the angle between the field and the normal to the plane of the loop is π/2 rad and increasing at 2.6 rad/s, what emf is induced in the loop?

Using a rope that will snap if the tension in it exceeds 387 N, you need to lower a bundle of old roofing material weighing 449 N from a point 6.1 m above the ground. Obviously if you hang the bundle on the rope, it will snap. So, you allow the bundle to accelerate downward. (a) What magnitude of the bundle's acceleration will put the rope on the verge of snapping?

T-mg = -ma

Why are most of the solutions out there is just T-mg = ma?

Since acceleration down, is opposite direction of T, why is the equation to solve this is not T-mg = - ma ?

William Tell shoots an apple from his son's head. The speed of the 118-g arrow just before it strikes the apple is 20 m/s, and at the time of impact it is traveling horizontally. If the arrow sticks in the apple and the arrow/apple combination strikes the ground 7.7 m behind the son's feet, how massive was the apple? Assume the son is 1.85 m tall.

A sphere with radius a has uniform charge/volume.

A metal sphere shell has inner radius b(from center) and outer radius c(from center).

Between a and b is empty.

Outer metal shell has total charge Q₁

_{Please start with Gauss's law and show steps}

Find Electric field in region

a) r<a

b)a<r<b

c)b<r<c

d) r>c

An astronomical telescope is being used to examine a relatively close object that is only 107.00 m away from the objective of the telescope. The objective and eyepiece have focal lengths of 1.470 and 0.0900 m, respectively. Noting that the expression M = - f_o/f_e is no longer applicable because the object is so close, use the thin-lens and magnification equations to find the angular magnification of this telescope.

The drawing shows a skateboarder moving at 6.60 m/s along a horizontal section of a track that is slanted upward by θ = 52.0° above the horizontal at its end, which is 0.700 m above the ground. When she leaves the track, she follows the characteristic path of projectile motion. Ignoring friction and air resistance, find the maximum height H to which she rises above the end of the track.