eric

Most popular questions and responses by eric
1. science

Which of the following gases was most likely present in Earth's earliest atmosphere? a. nitrogen b.hydrogen c.argon d.oxygen Help me please!

2. Physics

A rocket-powered hockey puck moves on a horizontal frictionless table. The figure below shows the graphs of vx and vy, the x- and y-components of the puck’s velocity. The puck starts at the origin. The graph of the X-velocity is v=8t cm/s and the

3. Math

The 3rd and 7th terms of an A.P are -1 and 11 respectively. Fine the nth term and the numbers of which must be added to get a sum of 430

4. Math

Which of the images above represents a proof of the Pythagorean Theorem? Explain your choice, and then explain how the figure proves the Pythagorean Theorem.

5. chemistry

Assuming equal concentrations, rank these aqueous solutions by their freezing point.? K2CO3, Li3PO4, Sn(ClO3)4, NH4I I tried to rank them according to the number of ions but i can't get it. highest freezing point --> lowest freezing point Sn(ClO3)4 ->

6. chemistry

A crystalline material containing 30 grams of barium chloride crystals was placed into an oven at 400 degrees c and heated for two hours. It was then cooled and weighed. the new mass was less than before it was heated, containing 20 grams if barium

7. physics

a 65kg person dives into the water from the 10m platform. she comes to a stop 2m below the surface of the water. what net force did the water exert on the swimmer? so for the net force i got -2548N i know: vf^2=vi^2 + 2ad vf^2 = 0 + 2(9.8)(10) vf^2 = 196

8. Math

Paul is painting a square wall with an area of 115 square feet. To the nearest foot, what is the length of the wall? Hint: A = s2. 11 29 42 58

9. physics

The same amount of heat entering identical masses of different substances produces different temperature changes. Calculate the final temperature when 1.25 kcal of heat enters 1.25 kg of the following, originally at 20.0°C. (a) water (b) concrete (c)

10. Physics-Trajectory

A particle's trajectory is described by x =(12t3−2t2)m and y =(12t2−2t)m, where t is in s. What is the particle's speed at t=0s ? What is the particle's speed at t=5.0s ? Express your answer using two significant figures. What is the particle's

11. Chem HELP!!

Which one of the following sets of quantum numbers can correctly represent a 3p orbital? a) (n = 3 l = 1, ml = 2) b)(n = 1, l = 3, ml = 3) c) (n = 3, l = 2, ml = 1) d) (n = 3, l = 1, ml = -1) e) (n = 3, l = 0, ml = 1)

12. Introduction to computers

Which Microsoft operating system started the process of authenticating users with a username and password

13. Physics

A massive steel cable drags a 20kg block across a horizontal, frictionless surface. A 100N force applied to the cable causes the block to reach a speed of 4.2m/s in a distance of 2.1m . What is the mass of the cable?

14. Physics

A ball of mass m makes a head-on elastic collision with a second ball (at rest) and rebounds with a speed equal to one-fourth its original speed. What is the mass of the second ball?

15. Chemistry

When carbon is burned in air, it reacts with oxygen to form carbon dioxide. When 26.4 g of carbon were burned in the presence of 82.1 g of oxygen, 11.7 g of oxygen remained unreacted. What mass of carbon dioxide was produced? Express your answer to one

16. Spanish

Are these correct? I. Rewrite each sentence by replacing the direct object in quotation marks with a direct object pronoun [me, te, lo, la, nos, los, las]. Ejemplo: No conozco "al jefe del departamento." --> No lo conozco. 1. Esa compañía vende "casas

17. ChemII

A saline solution is 0.9% NaCl. What masses of NaCl and water would be required to prepare 50. L of this saline solution? Assume that the density of water is 1.000g/mL and that the NaCl does not add to the volume of the solution.

18. Physics

When a 65 kg person climbs into a 1000 kg car, the car's springs compress vertically by 3.1 cm. What will be the frequency of vibration when the car hits a bump? Ignore damping.

19. Math

The population of town A increases from 1,346 to 1,500. In the same period, the population of town B increases from 1,546 to 1,800. a. Find the percent of increase in population for town A and for town B. b. Which town had the greater percent of increase?

20. Educational Technology and Online Learning

what is the purpose of the introduction in an expository essay

21. physics

A projectile is fired in such a way that its horizontal range is equal to 8.5 times its maximum height. What is the angle of projection?

22. physics

Rubbing your hands together warms them by converting work into thermal energy. If a woman rubs her hands back and forth for a total of 12 rubs a distance of 7.50 cm each and with a frictional force averaging 30.0 N, what is the temperature increase? The

23. physics

A firefighter a distance d from a burning building directs a stream of water from a fire hose at angle θi above the horizontal as in the figure. If the initial speed of the stream is vi, at what height h does the water strike the building? (Use theta for

24. physics

The engine of a large ship does 2.05 multiplied by 108 J of work with an efficiency of 4.00%. (a) How much waste heat (J) is produced? (b) How many barrels of fuel are consumed, if each barrel produces 6.00 multiplied by 109 J of heat when burned?

What are the Ka and/or Kb value for 1M ZnCl2 Show work please!!!

26. Chemistry

The vapor pressure, P, of a certain liquid was measured at two temperatures, T. Represented in a table: T (in Kelvin) ------- P(in kPa)  --------------- [4.00]  --------------- [8.59] What is the enthalpy of vaporization for this liquid? (Delta H

27. chemistry

A 141-mg sample was placed on a watch glass that weighed 9.203 g. What is the weight of the watch glass and sample in grams?

28. college physics

A(n) 13,300 lb railroad car traveling at 7.4 ft/s couples with a stationary car of 6790 lb. The acceleration of gravity is 32 ft/s^2. What is their velocity after the collision (ft/s)? And what impulse did the first car receive? Answer in units of lbs. Any

29. Math

Simplify (Log75+log9+log5)÷(log5+log45)

30. physics

In 1986 a gargantuan iceberg broke away from the Ross Ice Shelf in Antarctica. It was approximately a rectangle 160 km long, 45.0 km wide, and 250 m thick. (a) What is the mass of this iceberg, given that the density of ice is 917 kg/m3? (b) How much heat

31. Chemistry

A solution is made by dissolving 0.500 mol of HF in enough water to make 1.00 L of solution. At 21 C, the osmotic pressure of the solution is 1.35 atm. What is the percent ionization of this acid? This is what i did.. is it correct? (1.35 atm) =

32. physics

In a local bar, a customer slides an empty beer mug down the counter for a refill. The bartender is momentarily distracted and does not see the mug, which slides off the counter and strikes the floor at distance d from the base of the counter. The height

33. physics 11

A swimmer swims perpendicular to the bank of a 20.0 m wide river at a velocity of 1.3 m/s. Suppose the river has a current of 2.7 m/s [W]. (a) How long does it take the swimmer to reach the other shore? (b) How far downstream does the swimmer land from his

34. Math

What is the sqaure root of thirty six over forty nine?

35. Math

Thinking about the different types of numbers you learned in this unit, how would you help someone remember the differences between rational and irrational numbers? Remember to mention some of the Key Words from your lessons

36. physics

A magician pulls a tablecloth from under a 200 g mug located 30.0 cm from the edge of the cloth. The cloth exerts a friction force of 0.105 N on the mug, and the cloth is pulled with a constant acceleration of 3.50 m/s2. How far does the mug move relative

37. physics

A certain heat engine does 8.0 kJ of work and dissipates 8.00 kJ of waste heat in a cyclical process. (a) What was the heat input to this engine? (b) What was its efficiency?

38. physics

A hand-driven tire pump has a 2.50 cm diameter piston and a maximum stroke of 31.0 cm. (a) How much work (J) do you do in one stroke if the average gauge pressure is 2.40 multiplied by 105 N/m2 (about 35 psi)? (You may consider this an isothermal process.)

39. chemistry

a certain radioactive nuclide has a half life of 5.00 hour. Calcuate the decay rate for 1.000 mole of this nuclide __________ decay s-1

40. PHYSICS

TRACY SWIMS ACROSS A STREAM OF WIDTH 40.0M IN 33.0S WHEN THERE IS NO CURRENT.SHE TAKES 59.0 TO COVER THE SAME DISTANCE WHEN THERE IS CURRENT.FIND THE SPEED OF THE CURRENT RIVER.

41. math, economics, game theory

Two people have 10 dollars to divide between themselves. they use the following procedure. each person names a number of dollars (nonnegative integer), at most equal to 10. IF the sum of the amounts that the people name exceeds 10 and the amounts named are

42. statistics

Scores on the GRE​ (Graduate Record​ Examination) are normally distributed with a mean of 541 and a standard deviation of 101. Use the 68-95-99.7 Rule to find the percentage of people taking the test who score between 238 and 844 The percentage of

43. math

Mrs. Bollo's second grade class of thirty students conducted a pet ownership survey. Results of the survey indicate that 8 students own a cat, 15 students own a dog, and 5 students own both a cat and a dog. How many of the students surveyed own no cats?

44. physics

The "steam" above a freshly made cup of instant coffee is really water vapor droplets condensing after evaporating from the hot coffee. What is the final temperature of 280 g of hot coffee initially at 90.0°C if 2.50 g evaporates from it? The coffee is in

45. physics

(a) A rectangular gasoline tank can hold 41.0 kg of gasoline when full. What is the depth(m) of the tank if it is 0.400 m wide by 0.900 m long? (b) What is the volume(gal) of the tank? (It is suitable for a passenger car.)

46. accouting

Nancy Company has budgeted sales of \$300,000 with the following budgeted costs: Direct materials \$60,000 Direct manufacturing labor 40,000 Factory overhead Variable 30,000 Fixed 50,000 Selling and administrative expenses Variable 20,000 Fixed 30,000

47. Spanish

Are these correct? Thank you for helping Finish the following sentences including at least one possessive adjective (mi[s], tu[s], su[s], nuestro[s] or nuestra[s]) in your answer. Ejemplo: La profesora que tiene mi amiga es antipática, pero "mis

48. chemistry

E degrees (V) A galvanic cell based on the following half reaction s Au3+ 3e- ----> Au 1.50 Mg2+ 2e- ------> Mg -2.37 The cell is set up at 25 C with [Mg2+] = 1.00 x 10^-5 M The cell potential is observed to be 4.01 V. Calculate the [Au3+] that must be

49. physics

About 50,000 years ago, in an area located outside Flagstaff, Arizona, a giant 4.5x10^7 kg meteor fell and struck Earth, leaving a 180 m hole now known as Barrington crater. If the meteor was traveling 20000 m/s upon impact, with what average force did the

50. Chemistry

The specific heat of a certain type of metal is 0.128 J/(g-c). What is the final temperature if 305 J of heat is added to 86.9 g of this metal initially at 20 degrees C? Tfinal = ___ C

51. Physics

A soft drink can contains about 0.20 kg of liquid at 5 oC. Drinking this liquid can actually consume some of the fat in the body, since energy is needed to warm the water to body temperature (37 oC). How many kcal should the drink have so that it is in

52. Introduction to computers

You call the help desk to report a problem you are having on your computer. The technician asks you what operation system you are running. You know it is windows 7 but you forgot which version . How can you find out.

53. Physics

two skaters, each of mass 55 kg, approach each other along parallel paths separated by 3.8 m. They have opposite velocities of 1.9 m/s each. One skater carries one end of a long pole with negligible mass, and the second skater grabs the other end of it as

54. science

How do you calculate how long will it take an object dropped from a window to fall a distance of 78.4 meters?

55. Calculus

Find the value(s) of c guaranteed by the Mean Value Theorem for Integrals for the function over the given interval. f(x) = 4√x [4, 9]

56. Spanish

Are these correct? Answer the following questions using the present progressive. Be sure to answer with the same verb that is used in each question. 1. Creo que Xavier (1) _____ (2) __________ en la casa de sus padres mientras asiste a la Universidad.

57. statistics

Suppose 1,600 of 2,000 registered voters sampled said they planned to vote for the Independent candidate for president. Using the 0.95 degree of confidence, what is the interval estimate for the population proportion (to the nearest tenth of a percent)?

58. Chemistry

A 50.0-mL sample of 0.10 M HNO2 is titrated with 0.10 M NaOH. What is the pH after 25.0 mL of NaOH have been added?

59. Physics

Three positive point charges are located at the corners of a rectangle. Find the electric field at the fourth corner if q1 = 5 nC, q2 = 6 nC, and q3 = 7 nC. The distances are d1 = 0.6 m and d2 = 0.2 m. (Let the positive x-direction be to the right, and the

60. Chemistry

You have a 22L cylinder of helium at a pressure of 150atm and a temperature of 31C. How many ballons can you fill, each with a volume of 5.0L, on a day when the atmospheric pressure is 755mmHg and the temperature is 22C?

61. Math

Martin used some apples to make muffins.Omar used 5 fewer than half as many apples as Martin used

62. english

chick: a young woman A. direct definition B. indirect definition a

63. Algebra

Tell whether the lines for each pair of equations are parallel perpendicular of neither y=-3x+7 -2x+6y=3 Tell whether the lines for each pair of equations are parallel perpendicular of neither y=(-1/5)x=6 -2x+10y=5

64. physics

A 1.80 m radius playground merry-go-round has a mass of 120 kg and is rotating with an angular velocity of 0.300 rev/s. What is its angular velocity after a 19.0 kg child gets onto it by grabbing its outer edge? The child is initially at rest.

65. college

Two point charges have a total charge of 505 µC. When placed 1.10 m apart, the force each exerts on the other is 19.3 N and is repulsive. What is the charge on each? (Round your answers to the nearest µC.)

66. Math

A class has 27 students. Fifteen are boys and the rest are girls. What is the ratio of girls to total students? 12 : 15 15 : 12 27 : 12 12 : 27

67. Chemistry

You have a 22L cylinder of helium at a pressure of 150atm and a temperature of 31C. How many ballons can you fill, each with a volume of 5.0L, on a day when the atmospheric pressure is 755mmHg and the temperature is 22C? I know I use PV=nRT, but what

68. Chemistry

Using the equation: 2C2H6 + 7O2--> 4CO2 + 6H20 How many moles of CO2 are produced by the reaction of 21.0 mol O2? Again, not sure how to write it correctly, but if I multiply 7O2 by 3, then I should do the same to the other side of the equation to make it

69. physics

An ice bag containing 0°C ice is much more effective in absorbing heat than one containing the same amount of 0°C water. (a) How much heat in kcal is required to raise the temperature of 0.700 kg of water from 0°C to 27.0°C? (b) How much heat is

70. english

what does miss rosie symbolize in the poem miss rosie by lucille clifton?

71. Math

Nell made a pizza. she cut the pizza into fourths. then she cut each fourth. nell and her friens ate 6 of the smaller pieces of the pizza. What fraction of the pizza did Nell and her friends eat? What fraction of the pizza did Nell and friends Not eat?

72. Economics

The well known nationally syndicated columnist David Broder reported the recent findings of two academic political scientists. These scholars found that voters are quite turned off by negative campaigns of politicians. Many people went as far as not voting

73. physics

In 1986 a gargantuan iceberg broke away from the Ross Ice Shelf in Antarctica. It was approximately a rectangle 160 km long, 45.0 km wide, and 250 m thick. (a) What is the mass of this iceberg, given that the density of ice is 917 kg/m3? (b) How much heat

74. Algebra 2

Create an explicit equation for each recursively defined sequence below a1=17,an+1=an-7

75. math

A 10 kg quantity of a radioactive isotope decays to 3 kg after 17 years. Find the decay constant of the isotope.

76. Physics

Three forces are exerted on an object placed on a tilted floor. Forces are vectors. The three forces are directed as shown in the figure. If the forces have magnitudes F1 = 2.0 N, F2 = 17.0 N and F3 = 15.0 N, where N is the standard unit of force, what is

77. Algebra

Gymnast Clothing manufactures expensive soccer cleats for sale to college bookstores in runs of up to 500. Its cost (in dollars) for a run of x pairs of cleats is C(x) = 3000 + 9x + 0.1x2 (0 ≤ x ≤ 500). Gymnast Clothing sells the cleats at \$130 per

78. Economics

Thomas Schelling, an expert on nuclear strategy and arms control, observed in his book The Strategy of Conflict (Cambridge, MA: Harvard University Press, 1960), "The power to constrain an adversary depends upon the power to bind oneself." Explain this

79. history

Hamilton / Jefferson Readings Quiz 1. Alexander Hamilton thought that having a virtuous citizenry was a necessity in a Repulic. A) True B) False 2. Who said "The goodness of a government consists in a vigorous execution?" A) Thomas Jefferson B) Alexander

80. physics

One side of the roof of a building slopes up at 35.5°. A student throws a Frisbee onto the roof. It strikes with a speed of 15.0 m/s and does not bounce, but slides straight up the incline. The coefficient of kinetic friction between the plastic and the

81. physics

one ball is dropped off a cliff. A second ball is thrown down 1 second later with an initial speen of 40 ft/sec. How long after the second ball is thrown will the second ball overtake the first?.

82. Organic Chem

A 20 g mixture containing 95% (by weight) of A and 5% of B is recrystallized in toluene (b.p. 110 C). Solubility for compound A is 1.5 g @20 degrees and 10 g @ 110 degrees. For compound B solubility is 0.5 g @20 degrees and 8 g @ 110 degrees. What amount

83. french

how do you conjugate aimer mieux? do you just conjugate the aimer part?

84. chemistry

How much faster will neon effuse than krypton, given that the molar mass of krypton is 83.8 grams and that of neon is 20.18 grams?

85. College Physics

A concept question: Suppose that the centripetal force acting on an object in circular motion were increased to a new value, and the object remained in circular path with the same radius. How would its motion be affected?

86. Chemistry

How many calories are required at 0 degrees C to melt an ice cube with a mass of 25g? I got 2000 cal. Could you tell me if this is right?

87. Physics

One kind of slingshot consists of a pocket that holds a pebble and is whirled on a circle of radius r. The pebble is released from the circle at the angle θ so that it will hit the target. The angle in the drawing is 35.5°. The distance to the target

88. math

A 10 kg quantity of a radioactive isotope decays to 3 kg after 17 years. Find the decay constant of the isotope.

89. Math

Ann, Mara, Jenny, Tina, and Sue are sisters. Two of the five sisters must help their father at this business each Saturday. How many combinations of two sisters are possible?

90. Math

The new facility is the square in shape the link of one of the walls is 20 feet how many square feet is the facility

91. Math

How many inches represent 1 mile. Help 3/10 in = 7/8 mile

92. Calc

Find the critical numbers of the functions. f(0) = 2sec0 +tan0 on the interval [0,2pi]

93. math

A company made \$4 million in the second quarter. This is 1/3 more than it made in the first quarter and 4/5 of what it made in the third quarter. How much did the company make in the three quarters combined?

94. Yoku

A prism has total surface area of 360 m2 and volume of 60 m3. If the length, width, and height are reduced to half their original sizes, what will be the following?

95. Algebra

21. simplify (2sqrt5+3sqrt7)^2 show your work. Been confused on it for a while.

96. Physics

The intensity of a particular earthquake wave is measured to be 5.0 multiplied by 106 J/m2·s at a distance of 55 km from the source. (a) What was the intensity when it passed a point only 3.0 km from the source? (b) What was the rate energy passed through

97. math

Katrina is studying the effect of foreign substances on bacteria populations. If she introduces a beneficial substance, such as food, the bacteria population grows. If she introduces a harmful substance, such as a poison, the bacteria population decreases.

98. Physics

What will be the equilibrium temperature when a 245 g block of copper at 285 oC is placed in a 145 g aluminum calorimeter cup containing 825 g of water at 12.0 oC?