1. A powered model airplane of mass 1.77 kg is tied to a ceiling with string and allowed to fly at speed 0.44 m/s in a circular path of radius 0.44 m while suspended by the string which makes a constant angle with respect to the vertical. (a) What is the angle, in degrees, that the string takes such that the above is true? (b) What is the tension in the string, in N?

I have a hard time understanding the subject of fictitious forces. Let's discuss a few examples:

1) I'm sitting inside a vehicle which is accelerating in a straight line. I feel like someone is pushing me to the seat. So, on the one hand, I'm told that this happens according to the third Newton's law: this pressure is the result of me pushing the seat as a reaction to the seat pushing me (because it is accelerating with the same acceleration as the car). On the other hand, these forces are acting on different objects and I'm told that there is another fictitious force acting on me in an opposite direction to the acceleration. So what is right? And if there is a fictitious force, then why some call it a "math trick" when they are real and I can feel them?

2) I do not understand why some call centrifugal force a fictitious force. The earth is pulling the earth with its "invisible" string called gravitation. That's why the moon is still there. And this is the centripetal force. However the moon is also pulling the earth according to the Newton's third law, and that's why we have tides. This is the centrifugal force. So why it is fictitious? What it has to do with frame of reference? When we observe this in non-inertial frame of reference (such as the moon), does it simply mean that we can't call it anymore a reaction force according to the Newton's third law? But why if it is virtually the reaction force?

3) Accelerating elevator - similar to the first example - let's say the elevator is accelerating upwards. So we get that N? =m(g+a), and that's the same as me pushing the floor. That is why I feel heavier. Then why some add to here the fictitious force?

I will appreciate any answer.

make a table with three column, and write the similarities and differences for the three forces, 1. Gravitational Force 2. Colomb Force 3. Magnetic Force Make pictures to explain the differences.

Using the information provided in Lecture #3, compare the amount of energy released by chemical and nuclear reactions, given an identical mass of fuel. Describe two features of nuclear weapons design which reflect the physical differences between chemical and nuclear reactions.

In the figure, four charges, given in multiples of 5.00Ý10-6 C form the corners of a square and four more charges lie at the midpoints of the sides of the square. The distance between adjacent charges on the perimeter of the square is d = 3.60Ý10-2 m. What are the magnitude and direction of the electric field at the center of the square? The magnitude of E? Ex? Ey?

A ball of mass 500g is shot with an initial velocity of 10 m/s. the ball hits a pendulum bob (initially at rest) of mass of 2kg and the collision is perfectly elastic. a) find the velocity of the pendulum bob immediately after the collision. b) find the length of the pendulum if it comes to rest after turning by an angle of 30 degrees.

- Part b is the one I am stuck on!!!

A. Germanium is a semiconductor. If small amounts of the elements In, P, Sb, or Ga are placed into the Ge as impurities (not at the same time but in four separate instances) what types of semiconductors are manufactured in the four cases?

B. Normally, in conducting materials, we think of current as being carried by electrons as they move through a solid. In semiconductors, it is also common to talk about the current being carried by the “holes” in the valence band.

a. Explain how “holes” move through a solid material

b. If, in a p-type semiconductor device, electric current is moving from left to right, in which direction will the holes be moving?

A bullet of mass 2.7 g strikes a ballistic pendulum of mass 2.7 kg. The center of mass of the pendulum rises a vertical distance of 11 cm. Assuming that the bullet remains embedded in the pendulum, calculate the bullet's initial speed.

If the momentum of a particle is doubled, what happens to its de Broglie wavelength?

it decreases by a factor of 2^-1/2

it doubles

it halves

it becomes slightly less than half

it slightly more than doubles

A catapult launches a test rocket vertically upward from a well, giving the rocket an initial speed of 80.8 m/s at ground level. The engines then fire, and the rocket accelerates upward at 4.20 m/s² until it reaches an altitude of 990 m. At that point its engines fail, and the rocket goes into free fall, with an acceleration of −9.80 m/s². (You will need to consider the motion while the engine is operating and the free-fall motion separately.)

(a) For what time interval is the rocket in motion above the ground?

(b) What is its maximum altitude?

(c) What is its velocity just before it hits the ground?

A DC power line for a light-rail system carries 1000 A at an angle of 30.0o to the Earth’s 5.00×10−5 -T field.

What is the force on a 100-m section of this line? (b) Discuss practical concerns this presents, if any.

What is the maximum torque on a 150-turn square loop of wire 18.0 cm on a side that carries a 50.0-A current in a 1.60-T field? (b) What is the torque when θ is 10.9o?

The components of the electric field in an electromagnetic wave traveling in vacuum are described by
E_x = 0, E_y = 0, and
E_z = 2.84 sin(8.73x - ωt) V/m, where x is measured in meters and t in seconds. Calculate the frequency of the wave.

Calculate the wavelength of the wave.

Calculate the amplitude of the magnetic field of the wave.

Calculate the intensity of the wave.

The thermal conductivity of aluminium is kAl = 225W/(m·C), while that of iron is kFe = 75W/(m·C). Cubes of aluminium and iron are prepared with cross-sectional area A = 0.04m2 (i.e., 400 cm2) and thickness L = 0.2m.

(a) The aluminium cube is placed between a hot reservoir at TH = 80C and a cold reservoir at TC = 20C. Determine the rate at which heat flows through the aluminium cube.
(b) The iron cube is placed between a hot reservoir at TH = 80C and a cold reservoir at TC = 20C. Determine the rate at which heat flows through the iron cube.
(c) The two cubes are placed side-by-side (i.e., in parallel) between a hot reservoir at TH = 80C and a cold reservoir at TC = 20C. (i) Determine the effective thermal conductivity of this parallel arrangement of cubes. (ii) Determine the rate at which heat flows through the two cube in parallel.
(d) The two cubes are placed one-after-the-other (i.e., in series) between a hot reservoir at TH = 80C and a cold reservoir at TC = 20C. (i) Determine the effective thermal conductivity of this series arrangement of cubes. (ii) Determine the rate at which heat flows through the two cubes in series.