Physics Homework:

1) A 1400 kg car goes around the corner at a constant speed of 15.0 m/s. If the centripetal acceleration is 5.00 meters per second per second, what is the radius of the corner?

2) A 75 kg box is pushed across a level floor. If the force required to maintain constant velocity is 255 N, what is the coefficient of kinetic friction?

Choose the correct statements from the following list. (Give ALL correct answers, i.e., B, AC, BCD...)

A) A major difference between dark matter and dark energy is that one causes the univserse's expansion to slow down, the other to make it expand faster.
B) The critical density is the density needed to cause the Big Bang.
C) Assuming no dark energy, if the matter density of the universe is less than critical, the universe is open.
D) The inflationary model of the universe solves both the flatness and the horizon problems.
E) Assuming no dark energy, if the matter density of the universe is greater than critical, the universe is will expand forever.
F) Observations show us that the geometry of our universe must be very closed
G) The horizon problem in cosmology is that regions of the universe that should not have ever had thermal contact with one another have the same temperature.

Consider an RC circuit with E = 12.0 V ,R = 165 Ω , and C = 55.6 μF .

A) Find the time constant for the circuit.

B) Find the maximum charge on the capacitor.

C) Find the initial current in the circuit.

Friction between the skaters and the ice is negligible.

Ann has a mass of M, a moment of inertia of 3I_oand has a velocity of v_a = -2voi + 7voj. She is spinning with an angular velocity 10ω_o up.

Bob has a mass of 2M, a moment of inertia of 5I_o and has a velocity of vb = 4voi + voj. He is spinning with an angular velocity 2ω_o down.

The two ice dancers join together (collide) and hold onto each other taking time Δt for this to occur. Assume that the moment of inertia of the pair joined together is equal to the sum of their individual moments of inertia.

Answer the following questions in terms of M, I_o, v_o, ω_o,and Δt.

(A) What quantities are conserved during the collision (when the skaters join together)? List all conserved quantities that are useful to calculate the velocity and angular velocity after the collision.  

(B) What is the velocity of the pair after joining together? Write in component vector form.

(C) What is the y component of the average force that Ann exerts on Bob during the collision?

(D) What is the final angular velocity of the pair after joining together? (Give magnitude of the angular velocity and whether it is up or down.)

(E) What is the total rotational kinetic energy after the collision?

vector a has a magnitude of 16m and a direction of 65 above the negative x axis. vecot b has a madnitude of 9.0m and is directed along the negative x axis. find the magnitude and direction of A+B

There are n holes on the drywall and these n holes are on one horizontal line. You are using patches (each patch is with length 1) to cover these holes. What is the minimum number of patches that you have to use? Provide your algorithm and the correctness analysis.

Explain the astrometric method that astronomers use to search for other planetary systems that orbit a star.

NOTE: Please do not hand-write the answer as it is often difficult to read.

To complete this exercise you need a software package that allows you to generate data from the uniform and normal distributions.

(i) Start by generating 500 observations xi - the explanatory variable - from the uniform distribution with range [0,10]. (Most statistical packages have a command for the Uniform[0,1] distribution; just multiply those observations by 10.) What are the sample mean and sample standard deviation of the xi?

(ii) Randomly generate 500 errors, ui, from the Normal[0,36] distribution. (If you generate a Normal[0,1], as is commonly available, simply multiply the outcomes by six.) Is the sample average of the ui exactly zero? Why or why not? What is the sample standard deviation of the ui?

(iii) Now, generate the yi as

??=1+2??+??≡?0+?1??+??

that is, the population intercept is one and the population slope is two. Use the data to run the regression of yi on xi. What are your estimates of the intercept and slope? Are they equal to the population values in the above equation? Explain.

(iv) Repeat parts (i), (ii), and (iii) with a new sample of data, starting with generating the xi

??=0.5×??

Now what do you obtain for b0 and b1? Why are these different from what you obtained in part (iii)? Explain why in detail.

Which orbital properties of extrasolar planets can be measured and what methods are used to make those measurements? Please do not hand write or post pictures as it is difficult to read.. thanks!

A star is moving towards a moon. It has mass m = 0.22×109 kg and speed v1 = 2.6×107 m/s at distance R1 = 2.9×107 m from the center of the moon. The radius of the moon is R = 0.86×107 m. The mass of the moon is M = 8.8×1025 kg. no air is around the moon.

a. Calculate the gravitational potential energy PE1 of the star at R1. potential energy is zero at infinity.

b. Calculate the total energy E1 of the star at R1.

c. Calculate the total energy E of the meteoroid at R, the surface of the moon.

d. Calculate v, the meteoroid’s speed at the moons surface

a. It has been said the energy from the sun is based on fusion. Explain, using reaction equations.  Are the other stars the same then?

b. Fission reactors have to be designed with caution toward harmful radiation and contamination. Do Fusion reactors have these same harmful “radiation” problems? Why or why not?

A 28 kg block on a horizontal surface is attached to a horizontal spring of spring constant k = 2.9 kN/m. The block is pulled to the right so that the spring is stretched 8.4 cm beyond its relaxed length, and the block is then released from rest. The frictional force between the sliding block and the surface has a magnitude of 37 N. (a) What is the kinetic energy of the block when it has moved 2.7 cm from its point of release? (b) What is the kinetic energy of the block when it first slides back through the point at which the spring is relaxed? (c) What is the maximum kinetic energy attained by the block as it slides from its point of release to the point at which the spring is relaxed?

A 1.00 cm-high object is placed 3.40 cm to the left of a converging lens of focal length 8.95 cm. A diverging lens of focal length −16.00 cm is 6.00 cm to the right of the converging lens. Find the position and height of the final image.

position
Take the image formed by the first lens to be the object for the second lens and apply the lens equation to each lens to locate the final image. cm  ---Select--- behind the second lens in front of the second lens height
Calculate the magnification produced by each lens. Then consider how the magnification relates image size and object size for each lens to find the height of the final image. cm

Is the image inverted or upright?

uprightinverted    

Is the image real or virtual?

realvirtual    

(b)

What If? If an image of opposite characteristic, i.e., virtual if the image in part (a) is real and real if the image in part (a) is virtual, is to be obtained, what is the minimum distance (in cm), and in which direction, that the object must be moved from its original position?

distance cmdirection ---Select--- to the left to the right