A negative charge Q1 = -5.00 mC is located at a point X1 = -1.00 m, a positive charge Q2 = 8.00 mC is located at a point X2 = 3.00 m and a negative charge Q3 = -12.00 mC is located at a point X3 = 7.00 m.a. Draw free body diagrams for the electric force acting on Q1, Q2, and Q3.b. Find the magnitude of the force between Q1 and Q2.c. Find the magnitude of the force between Q1 and Q3.d. Find the magnitude of the force between Q2 and Q3.e. Find the magnitude and direction of the net electric force on charge Q1.f. Find the magnitude and direction of the net electric force on charge Q2.g. Find the magnitude and direction of the net electric force on charge Q3.

1. The Cosmic Microwave Background and Prizewinning Cosmology

(a) How can we see the CMB if the photons were released 14 billion years ago? Shouldn't those photons be billions of light years away by now?

(b) Who was awarded the 2006 Nobel Prize for Physics? What was the prize for-- what were the results, and how were they obtained?

(c) Why are these results from part (b) important?

Write the following vector in the component form and add them.

F₁ = 15 N at 60^o, F₂ = 20 N at 150^o, and F₃ = 30 N at 260^o.

A person jumps odd the top of a building which is 12 metres above ground. She is attached to the end of the bungie cord (a big rubber band) that has an unstretched length of 6 metres. The cord stretches until the physics major is stopped 2 metres above the ground. She then bounces back upward and begins oscillating (bouncing up and down). The student's mass is 55kg. Ignore air resistance. a) what is student's total energy after oscillations begin? b) what is spring constant k for bungie cord? c) what is frequency of her oscillation? d) how long does it take her to travel up and down 4 times ( how long does it take her to complete 4 oscillation)? e) what is the amplitude of resulting oscillation? f) what is her maximum speed after the oscillation begins?

In the Force lab, we use a small lab car with mass m=5 Kg, the experiment is on a horizontal table, on the car is acting a pulling force F= 20 N and the kinetic friction force Fr is acting as well. The car initially is at rest, and take 6.0 seconds to reach the velocity of 8.5 m/s.

a)       Calculate the magnitude of the friction force Fr acting on the car?

b)      We remove the pulling force when the car reaches the velocity of 8.5 m/s. What will be the total distance travelled by the car before stop? (From t=0 seconds until stop)

c)       What is the kinetic coefficient of friction?

(Practical magnetism) As we will see in lab, the magnitude ?? of the magnetic field of a permanent magnet drops with distance d so that ?? ∝ 1/? 2 when d is less than the size of the magnet (where you “feel” only the closest pole) but ?? ∝ 1/? 3 farther away (where both poles “blur together” and the field is weaker). (a) Could a coin-sized magnet in your wallet or purse erase the magnetic strip on your credit card or hotel room key? Suppose the magnet is 2 mm thick, and measure d from its center. Consider both a fridge magnet (?? = 5 mT at the surface) and a neodymium coin magnet (?? = 1 T at the surface). To erase a magnetic strip requires 4000 G for a “high-coercivity” (“HiCo”) card such as a credit card, but only 300 G for a “low-coercivity” (“LoCo”) card such as a hotel room key. (b) If so, how far apart should you keep them? (c) Could wearing a “magnetic stone” (with field strength comparable to a fridge magnet) affect your health? To answer this, ask yourself whether people’s health is affected by the Earth’s magnetic field, of strength about 0.2 G? At what distance from the stone do you experience this same field strength?

A physics book was thrown from the top of a library with a speed of 8.0 m/s at angle 60o with the horizontal. After 5 seconds, the book hits the ground:

(a) Find the height of the library above the ground.
(b) Find the distance of the point where the book falls on the ground from the base of the library.

(c) Just before the book hits the ground, find the horizontal and vertical components of its velocity.

The cube in the figure below has 5 sides grounded and the other side is held at a potential Vo. What is the potential at the center of the cube?

P.S. "The other side" is the right face of the cube. I can't upload the image for some weird reason.

A wheel, released from rest, is rotating with constant angular acceleration. After 8.0 seconds, its speed reaches to 12 rev/sec (a) what is its angular acceleration? (b) Through what angle has the wheel turned? (c) How many revolutions has it completed in 8.0 second?

The tires of a car make 92 revolutions as the car reduces its speed uniformly from 87.0 km/h to 61.0 km/h. The tires have a diameter of 0.86 m.

Part A) What was the angular acceleration of the tires?

Part B) If the car continues to decelerate at this rate, how much more time is required for it to stop?

Part C) If the car continues to decelerate at this rate, how far does it go? Find the total distance.

A mass weighing 8 lb stretches a spring 1/2 foot. Then mass is initially released from rest at a point 1

foot above the equilibrium.

a) Solve the equation of motion with no damping.

Use the same spring system and initial conditions as in Problem above. The spring system is now placed in

a medium that offers a damping force equal to 2 times the instantaneous velocity.

b) Solve the equation of motion

c) At what time does the mass go downward through the equilibrium for the first time?

Explain how the Scientific Revolution, including the so-called Copernican Revolution, and its validation via Galileo’s astronomical observations impacted Aristotle’s realist empiricist epistemology.

We’re going to think about other possible sources for magnetic fields. Recall that the source of magnetic fields in permanent magnets is aligned electron orbits(electrons going in circles all the same direction so the circles are parallel and they are either all traveling clockwise or counter clockwise).

1. Where do electric fields come from? Draw an electric field diagram for each of the two types of source.
2. Pick a spot in one of your field diagrams. How would you determine the electric field there (There’s an equation we used that is closely related to the force on a charge there)? Now, take the same point, but move your source an inch to the right. What is the electric field at that point now?
3. Now, an electron orbit generates a magnetic field. What else does it generate (this is directly related to the answer of question 2)? Is that second thing static (constant) or time-dependent (moving)?
4. Now, why might a circuit generate a magnetic field (Think about questions 2 and 3)? Why?
5. If you wanted to make a wire generate a big magnetic field, how might you design it and why (There are many ways to get to this conclusion)? Congratulations, you have designed an inductor. Place this object in a circuit and it will prevent changes in current.

Transverse waves on a string have wave speed v = 8.00 m/s, amplitude A = 0.0700 m, and wavelength λ = 0.320 m. The waves travel in the -x direction, and at t = 0 the x =0 end of the string has its maximum upward displacement.

1) Find the frequency of these waves.

2) Find the period of these waves.

3) Find the wave number of these waves.

4) Write a wave function describing the wave. Express your answer in terms of x and t. Use π as constant.

5) Find the transverse displacement of a particle at x = 0.360 m at time t = 0.150 s. Express your answer in meters.

6) How much time must elapse from the instant in part E until the particle at x = 0.360 m next has maximum upward displacement? Express your answer in seconds.