The conductivity of carbon is about 3*(10^4) S/m.

a. What size and shape sample of carbon has this conductance? (Conductance is equal to 1/R).

b. What is the conductance if every dimension of the sample found in (a) is cut in half?

82Rb with T1/2=1.25min, like 81Rb is a positron emitter that is useful for heart perfusion imaging. It can be produced by the natural decay of 82Sr  (T1/2=25 days).

1) Suppose you have a sample of with 100 mCi of 82Sr. When will the activity of 82Rb reach over 99% of the activity of 82Sr?

2) How much daughter activity (Question 1) will there be after 20 minutes?

3) How much daughter activity (Question 1) will there be after 20 days?

1) Assuming you start with 1 mCi 52Fe and no 52mMn, what will the activity of 52mMn be after 10 min? Answer in mCimCi.

2) What will be the activity in previous question after 20 minutes?

3) When will the activity of the sample be the highest, i.e. when is the best time to elute the sample?

4)Over the weekend there is no one working to elute the sample. Assuming you start with 10¹⁰ Bq of 52Fe and no 52mMn, what will the activity of 52mMn be after 48 hours?

5) What is the activity of the 52Fe in Question 4 at this point?

a. Explain the differences between analogue and digital signals and systems. Use sketches to support your explanations.
b. Explain the characteristics of an amplifier of your choice, using supporting sketches.
c. Draw and explain the operation of a simple circuit of your choice which uses at least three logic gates.
d. Describe a situation where;
(a)   An analogue circuit would be appropriate, and why a digital circuit would not.
(b)   A digital circuit would be appropriate, and why an analogue circuit would not.

Please answer all of them asaappp

Three charges of +Q are at the three corners of a square of side length L. The last corner is occupied by a charge of -Q. Find the electric field at the center of the square.

A 5.0mm diameter hole is 1.0m m below the surface of a 2.0m diameter tank of water. What is the rate, in mm/min, at which the water level will initially drop if the water is not replenished?

answer in mm/min

You push a 2 kg block down a ramp. You apply a force of 9 N that is directed along and down the ramp with a coefficient of kinetic friction of 0.20. The block travels from rest to 4 m/s over a distance of 2 meters. Use g = 10 m/s/s. Report using 3 significant digits.

How many Newton's second law equations can you write for this problem?

Group of answer choices

4

3

2

1

How many forces are on the block?

Group of answer choices

2

1

4

3

What is the magnitude of the acceleration of the block?

What is the angle of the ramp? (in degrees)

(a) Describe the behaviour of positive and negative charges within a p-n junction. Use a sketch/sketches (drawn by hand) to support your description.
(b) Show your knowledge and understanding of the actions involved with the following devices;
(i) A diode
(ii) A bipolar transistor
(iii) A MOSFET
(c) Use semiconductor theory to describe the movement of charge carriers in each of the three devices given in Task (b).
(d) For each of the devices given in Task (b) make a judgement about their performance limitations. Also give a typical application for each of the devices.

Please answer all of them asapppp

This lab uses three friction carts with different surfaces on the bottom (cork, felt, and Teflon) and a set of masses totaling 1250 g. The carts are pulled with a piece of string attached to a hook on a force sensor, which measures the force of tension in the string. Behind the cart being pulled is a motion sensor. These two devices are used to display and record the string tension and the velocity of the cart as a function of time, with a 20 Hz (measurements per second) sampling rate. The main use for the velocity vs. time graph is to allow the person pulling the cart to make sure that, once the cart starts to move, they are pulling the cart with the constant force required to maintain a constant velocity.

1. Before the cart starts moving, what is the net force on it? How is the (horizontal) string tension force acting on the cart related to the friction force acting on the cart?

2. When the cart is moving with a constant velocity, what is the net force on it? How is the (horizontal) string tension force acting on the cart related to the friction force acting on the cart?

1. Kingda Ka is one of Six Flags famous roller coasters. It does not have a running engine. A hydraulic launcher “shoots” the roller coaster with an initial velocity of 57 m/s and relies on the conservation of energy to take care of the rest until the end of the ride. The first hill that the roller coaster goes over is 127 meters above the original launch height. After the coaster returns to the original launch height, it goes over a second hill of 39 meters above the launch height, before slowly coming to a stop. The mass of the coaster with its riders is approximately 2200 kg. Assume no air resistance and no friction for the time being and its launch height to be 0m.

a. How much potential energy does the coaster, with its riders, have right after it is shot out by the hydraulic launcher?

b. Determine the kinetic energy a coaster, with its riders, has right after it is shot out by the hydraulic launcher.

c. Determine the potential energy a coaster, with its riders, has at the top of the 127m hill?

d. Determine the kinetic energy a coaster, with its riders, has at the top of the 127m hill?

e. At what speed does the coaster, with its riders, travel at top of the first hill?

f. Determine the potential energy a coaster, with its riders, has at the top of the 39m hill?

g. Determine the kinetic energy a coaster, with its riders, has at the top of the 39m hill?

h. At what speed does the roller coaster travel over the second hill?

i. What is the slowest speed that the roller coaster must be launched at in order to get it over the first hill? (Again, neglect friction and air resistance.)

Discuss the technical and social aspects of the possibility that solar power could be a major energy source for the future of mankind

Please, answer below questions:

Remember units. Use the correct number of significant figures.

1. A laser produces a beam of light with a radius of 1.7 mm. Its energy density is 9.17 10-7 J/m3 . a) What is its power? b) What is the force of its radiation pressure?

2. As light goes from air to an unknown liquid, an incident angle of 20.0° becomes a refracted angle of 13.1°. If light goes from the unknown liquid to air, what is the largest incident angle that does not experience total internal reflection?

two turning forks have the same amplitude but diffrerent frequency. at the same time produce a comx wave . what is tthis called ?

if the period of the compelx wave that produce 0.25s and the period of one of the turning fork is 0.04s what is one possible frequency of the other turning fork ?

when the sinusoidal waves from the tuning forks are in opposite phases, what happens at those points to the complex wave they produce ?  

1. Imagine that the energy generation rate in the center of the Sun were suddenly to decrease.

How would the size of the core, and hence density, change in response to changes you described in your answer to the previous question?

2.How would the density change in the previous question in turn affect the energy generation rate and hence the temperature?

3. Put your answers to the three previous questions together to explain how the Sun maintains a perfect structural balance.