An electric motor exerts a constant torque of τ=10N⋅m on a grindstone mounted on its shaft; the moment of inertia of the grindstone is I=2.0kg⋅m2. If the system starts from rest, find the work done by the motor in 8.0 s and the kinetic energy at the end of this time. What was the average power delivered by the motor? Part A:Suppose we now turn off the motor and apply a brake to bring the grindstone from its greatest angular speed of 36 rad/s to a stop. If the brake generates a constant torque of 13 N⋅m , find the total work done (including signs) needed to stop the grindstone. Part A:Suppose we now turn off the motor and apply a brake to bring the grindstone from its greatest angular speed of 36 rad/s to a stop. If the brake generates a constant torque of 13 N⋅m , find the total work done (including signs) needed to stop the grindstone. Part B:Find the average power (including signs) needed to stop the grindstone in Part A.

Given is the rod of length L with the linear charge of density ?=?/? . The rod lies on the x axis with its midpoint at the origin. Find the electric field vector on y axis resulting from such continuous system of charge at distance y from the origin. Use this result to obtain the expression for electric field at distance y from the infinitely long wire.

1. In terms of edges, why is it an advantage to use mirrors over lenses in telescopes?

2. How does the placement of the eyepiece with Newtonian and Cassegrain reflectors differ?

3. What does the diffraction limit of a telescope depend upon?

Imagine that you have placed a compass due east of of a wire where current equals 2A (the wire is vertical and current travels from bottom to top).

1. If you turn the current on, how would the compass respond? (Does it change cardinal direction?)

2. How does the magnitude and direction of the total magnetic field change?

PLEASE EXPLAIN!

A neutron star has a mass of 3.35 × 1030 kg (about the mass of our sun) and a radius of 6.09 × 103 m. Suppose an object falls from rest near the surface of such a star. How fast would it be moving after it had fallen a distance of 0.013 m? (Assume that the gravitational force is constant over the distance of the fall, and that the star is not rotating.)

A neutron star is an astrophysical object having a mass of roughly 2.8 × 10³⁰ kg (about 1.4 times the mass of the sun) but a radius of only about 12 km. If you were in a circular orbit of radius 320 km (about 200 mi), how long would it take you to go once around the star? Show all steps and give reasoning.

2.00-nF capacitor with an initial charge of 5.35 µC is discharged through a 1.23-kΩ resistor.

(a) Calculate the current in the resistor 9.00 µs after the resistor is connected across the terminals of the capacitor. (Let the positive direction of the current be define such that

> 0.)

How is the instantaneous current related to the potential difference across the capacitor? mA

(b) What charge remains on the capacitor after 8.00 µs?

µC

(c) What is the (magnitude of the) maximum current in the resistor?
A

How would you construct a pendulum clock that is reliable under a variety of temperatures?

The binding energy of an electron in the ground state in a hydrogen atom is about:

A. 13.6 eV

B. 3.4 eV

C. 10.2 eV

D. 1.0 eV

E. 27.2 eV

A 4.4 x 10^14 Hz laser emits a 2.1

a. A large solenoid with a length of 6.7 m and 31000 turns of wire carries an initial current of 4.9 A. The solenoid is aligned so that the magnetic field is produces points to the East. A small coil of wire with a radius of 0.056 m and 2 turns of wire is placed inside this solenoid so that the normal to the plane of the coil is aligned with the axis of the solenoid. The current in the solenoid is then reduced to 0.57 A over a period of 2.4 s. What is the initial magnitude of the magnetic field inside the solenoid?

b. What is the initial magnetic flux through the coil?

c. What is the final magnitude of the magnetic field inside the solenoid?

d. What is the final magnetic flux through the coil?

e. If the coil of wire has a resistance of 31 Ω, what is the induced current in the coil? What is the magnitude of the average electromotive force (EMF) induced in the coil while the magnetic flux is changing?

f. If you are looking at the solenoid and coil from the East (so you are facing West) then the direction of the current in the solenoid must be _____ and the induced current in the coil will be ________

As shown in the figure (Figure 1) , a superball with mass m equal to 50 grams is dropped from a height of hi=1.5m . It collides with a table, then bounces up to a height of  hf=1.0m . The duration of the collision (the time during which the superball is in contact with the table) is tc=15ms . In this problem, take the positive y direction to be upward, and use g=9.8m/s2 for the magnitude of the acceleration due to gravity. Neglect air resistance.

Find the y component of the momentum, pbefore,y, of the ball immediately before the collision.

Find the y component of the momentum of the ball immediately after the collision, that is, just as it is leaving the table.

Find Jy, the y component of the impulse imparted to the ball during the collision.

Find the y component of the time-averaged force Favg,y, in newtons, that the table exerts on the ball.

Find Kafter?Kbefore, the change in the kinetic energy of the ball during the collision, in joules.

1. Using the two equations below, show that the final position of the monkey and ball are the same because of the acceleration due to gravity. At the final position of the monkey and ball, the height of both will be the same. They will also have the same time (t) since they will collide simultaneously. Please arrange your work in an orderly fashion so it may be graded accordingly.

2.      How long would it take a projectile shot from a cannon at 145 m/s, aimed at 45° above the horizon, to reach an altitude of 120 m?

3. If the initial velocity of the above cannon were adjustable, what velocity would be required to shoot the ball exactly a distance of 100 m? Use the following equation and solve:

4. The US Army and Marine Corps use a 39-caliber artillery weapon called the
Ultra-light-weight Field Howitzer (UFH). It fires a projectile at 827 m/s. What is the weapon’s maximum range in combat? (Use the above equation from problem 3)

5.What would be the effect of firing a projectile in space? What would be its trajectory? Explain your answers.?

Copy and paste the following questions in the submit box below and find the location where the following information is found:

Give the line numbers where the hypothesis occurs.
Give the line numbers where the experiment is described.
Give the line numbers where the results are presented.
Do you see signs of pseudoscience in this article, if so, Give the line numbers. Briefly describe the graph:

1. 1 Pesticides suspected in mass die-off of bees Text excerpted from March 29, 2012|By Eryn Brown, Los Angeles Times

2. 2 Scientists have identified a new suspect in the mysterious die-off of bees in recent years � a class of

3. 3 pesticides that appear to be lethal in indirect ways. The chemicals, known as neonicotinoids, are designed

4. 4 to target a variety of sucking and chewing insects, including aphids and beetles. Bees are known to ingest

5. 5 the poison when they eat the pollen and nectar of treated plants, though in doses so tiny that it was not

6. 6 seen as a threat.

7. 7 A study published online Thursday by the journal Science indicate that the pesticides are not altogether

8. 8 benign. The study used miniature radio frequency chips to track honeybees and found that the pesticide

9. 9 impaired their ability to navigate back to the hive after a feeding expedition.

10. 10 Beekeepers became alarmed that honeybees were vanishing from their nests across the U.S. in the fall of

11. 11 2006 � victims of a perplexing and pervasive malady now known as colony collapse disorder that wiped

12. 12 out as many as 90% of bees, in some cases. Scientists don't know exactly why the ailment strikes, but

13. 13 they believe it results from a combination of habitat degradation, infection by pathogens and parasites and

14. 14 pesticide use. Researchers have also documented sharp declines in bumblebees, which are important crop

15. 15 pollinators but are not domesticated.

16. 16 Neonicotinoid pesticides were developed to eradicate insects without threatening mammals. The

17. 17 chemicals, which are incorporated into the tissues, leaves and flowers of plants, target the central nervous

18. 18 system, leading to paralysis and death. Farmers began using them in the early 1990s.

19. 19 Past studies have explored effects of neonicotinoids in the lab, finding that they might harm bees'

20. 20 memory, learning and orientation. But the new study is among the first to examine the pesticides' effects

21. 21 on bees under real-world conditions.

22. 22 The study led by researchers from the French National Institute for Agricultural Research, or INRA,

23. 23 focused on honeybees, which have been victimized by colony collapse disorder throughout the Northern

24. 24 Hemisphere.

25. 25 First they glued special radio frequency identification tags to the bees' thoraxes. Then they fed the bees

26. 26 sublethal doses of a neonicotinoid and monitored the insects as they attempted to return to the hive.

1. 27 The research team discovered that the "intoxicated" bees were about twice as likely as unexposed bees to

2. 28 die because they couldn't find their way home. Computer simulations suggested that these no-shows could

3. 29 cause hive populations to crash in a matter of weeks, said study coauthor Mickael Henry, a researcher at

4. 30 INRA in Avignon. The weakened colonies would be especially vulnerable to environmental

5. 31 stresses such as climate change or disease, he added.

32

1. 33 The new findings lend support to the notion that pesticides contribute to colony collapse, but

2. 34 leave open the likelihood that habitat destruction and illness play a role too, scientists said.

3. 35 "There are a whole lot of things that stress the honeybees," said Eric Mussen, a honeybee

4. 36 specialist at UC Davis. "You can't point your finger at one thing and say, 'That is the problem.' "

5. 37 Mussen cautioned against singling out neonicotinoids when other pesticides could have similar

6. 38 effects on bees. Besides, he said, many insects have built up immunity to neonicotinoids, so

7. 39 farmers are likely to switch to different pesticides anyway.

B: Bees released at a random location a kilometer away from the hive. Vertical axis shows relative number of bees returning to hive (1 = 100%)

Graph from: Henry, M., Beguin, M., Requier, F., Rollin, O., Odoux, J., Aupinel, P., Aptel, J., Tchamitchian, S., & Decourtye, A. (2012). A Common Pesticide Decreases Foraging Success and Survival in Honey Bees Science

In the figure, the top tank, which is open to the atmosphere, contains water and the bottom tank contains oil covered by a piston. The tank on the right has a freely movable partition that keeps the oil and water separate. The partition is a vertical distance 0.10 m below the open surface of the water. If the piston in the bottom tank is 0.50 m below the open surface of the water and has a surface area of 8.3 x 10-3 m2, what must the mass of the piston be to keep the system in mechanical equilibrium. For simplicity, ignore the mass of the partition.