A cyclist rides 6.2 km east, then 9.28 km in a direction 27.27 degrees west of north, then 7.99 km west.
A. What is the magnitude of the total displacement, in km?
B. What is the direction of the displacement, measured in degrees west of north?
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A 3.0 m length of wire is made by welding the end of a 100 cm long silver wire to the end of a 200 cm long copper wire . Each piece of wire is 0.80 mm in diameter. The wire is at room temperature, so the resistivities are as given in the table below. A potential difference of 5.0 V is maintained between the ends of the 3.0 m composite wire.
(a) What is the current in the copper section?. A
(b) What is the current in the silver section? A
(c) What is the magnitude of vector E in the copper? V/m
(d) What is the magnitude of vector E in the silver? V/m
(e) What is the potential difference between the ends of the sliver section of wire? V
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|
A 20 km long, 230 kV aluminum transmission line delivers 33 MW to a city. |
A) If we assume a solid cylindrical cable, what minimum diameter is needed if the voltage decrease along this run is to be no more than 1.0 % of the transmission voltage? The resistivity of aluminum is 2.7×10−8Ω⋅m.
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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 Pesticides suspected in mass die-off of bees Text excerpted from March 29, 2012|By Eryn Brown, Los Angeles Times
2 Scientists have identified a new suspect in the mysterious die-off of bees in recent years � a class of
3 pesticides that appear to be lethal in indirect ways. The chemicals, known as neonicotinoids, are designed
4 to target a variety of sucking and chewing insects, including aphids and beetles. Bees are known to ingest
5 the poison when they eat the pollen and nectar of treated plants, though in doses so tiny that it was not
6 seen as a threat.
7 A study published online Thursday by the journal Science indicate that the pesticides are not altogether
8 benign. The study used miniature radio frequency chips to track honeybees and found that the pesticide
9 impaired their ability to navigate back to the hive after a feeding expedition.
10 Beekeepers became alarmed that honeybees were vanishing from their nests across the U.S. in the fall of
11 2006 � victims of a perplexing and pervasive malady now known as colony collapse disorder that wiped
12 out as many as 90% of bees, in some cases. Scientists don't know exactly why the ailment strikes, but
13 they believe it results from a combination of habitat degradation, infection by pathogens and parasites and
14 pesticide use. Researchers have also documented sharp declines in bumblebees, which are important crop
15 pollinators but are not domesticated.
16 Neonicotinoid pesticides were developed to eradicate insects without threatening mammals. The
17 chemicals, which are incorporated into the tissues, leaves and flowers of plants, target the central nervous
18 system, leading to paralysis and death. Farmers began using them in the early 1990s.
19 Past studies have explored effects of neonicotinoids in the lab, finding that they might harm bees'
20 memory, learning and orientation. But the new study is among the first to examine the pesticides' effects
21 on bees under real-world conditions.
22 The study led by researchers from the French National Institute for Agricultural Research, or INRA,
23 focused on honeybees, which have been victimized by colony collapse disorder throughout the Northern
24 Hemisphere.
25 First they glued special radio frequency identification tags to the bees' thoraxes. Then they fed the bees
26 sublethal doses of a neonicotinoid and monitored the insects as they attempted to return to the hive.
27 The research team discovered that the "intoxicated" bees were about twice as likely as unexposed bees to
28 die because they couldn't find their way home. Computer simulations suggested that these no-shows could
29 cause hive populations to crash in a matter of weeks, said study coauthor Mickael Henry, a researcher at
30 INRA in Avignon. The weakened colonies would be especially vulnerable to environmental
31 stresses such as climate change or disease, he added.
32
33 The new findings lend support to the notion that pesticides contribute to colony collapse, but
34 leave open the likelihood that habitat destruction and illness play a role too, scientists said.
35 "There are a whole lot of things that stress the honeybees," said Eric Mussen, a honeybee
36 specialist at UC Davis. "You can't point your finger at one thing and say, 'That is the problem.' "
37 Mussen cautioned against singling out neonicotinoids when other pesticides could have similar
38 effects on bees. Besides, he said, many insects have built up immunity to neonicotinoids, so
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
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A spelunker is surveying a cave. He follows a passage that goes 179 m straight west, then 211 m in a direction 45° east of south, then 285 m at 30° east of north. After a fourth unmeasured displacement he finds himself back where he started. Use a scale drawing to determine the fourth displacement.
| a) magnitude | _______ m |
| b) direction |
_______° SELECT ONE -----> : (north of east) (south of east) (south of west) (north of west) |
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If a pluck on a guitar is restricted and you hear a click rather than a steady long tone, how is that a wider frequency bandwidth?
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In a physics lab students are conducting an experiment to learn about the heat capacity of different materials. The first group is instructed to add 1.5-g copper pellets at a temperature of 92°C to 235 g of water at 16°C. A second group is given the same number of 1.5-g pellets as the first group, but these are now aluminum pellets. Assume that no heat is lost to or gained from the surroundings for either group.
(a) If the final equilibrium temperature of the copper pellets and water is 23°C, how many whole pellets did the first group use in the experiment? The specific heat of copper is 0.0924 kcal/(kg · °C).
(b) What is the equilibrium temperature of the aluminum and water mixture for the second group?
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a) please .. Describe the anatomy of a wave with respect to its amplitude, wavelength, frequency and time period with the help pf a suitable diagram.
b) Explain Doppler effect in detail with pictorial elaboration.
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A door 1.00 m wide and 2.30 m high weighs 330 N and is supported by two hinges, one 0.70 m from the top and the other 0.70 m from the bottom. Each hinge supports half the total weight of the door.
Part A:
Assuming that the door’s center of gravity is at its center, find the horizontal component of force exerted on the door by hinge on the top.
Ftop h=..... N
Part B:
Find the horizontal component of force exerted on the door by hinge on the bottom.
Fbottom h = ......N
(I got 127 N and -127 N but it still incorrect)
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In 1923, the United States Army (there was no U.S. Air Force at that time) set a record for in-flight refueling of airplanes. Using two refueling planes, an Airco DH-4B biplane was able to remain in flight for 37 hours. During the flight, the refueling planes were able to air-transfer a total of 687 gallons of fuel to the plane in 9 refueling transfers. Assume that the refueling nozzle had a diameter of 1.25 inches and each refueling took 2.43 minutes to perform. Calculate the velocity of the fuel through the nozzle. Assume that the fuel filled the entire cross-sectional area of the nozzle.
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A) An atom of iron-56, which consists of 30 neutrons, 26 protons, and 26 electrons, has a mass of 55.9349375 u. Calculate the mass defect for iron-56.
B) Convert the mass defect to energy.
C) Determine the average binding energy per nucleon for iron 56 (in MeV/nucleon).
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Lemur and Chimp find a 200-kg treasure chest filled with gold plated bananas. The chest rests on an incline as illustrated below. The coefficient of friction between the chest and incline is 0.60. The incline makes a 35 degree angle with the horizontal. A cord parallel to the incline prevents the box from moving. A) What are the possible tensions in the cord? B) After Lemur cuts the cord, what is the magnitude of the acceleration of the treasure chest? C) What is the speed of the treasure chest after sliding 30 m down the incline?
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2.3 g of helium at an initial temperature of 290 Kinteracts thermally with 7.4 g of oxygen at an initial temperature of 600 K .
a.What is the initial thermal energy of each gas?
b.What is the final thermal energy of each gas?
c.How much heat energy is transferred, and in which direction?
d.What is the final temperature?
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