# Justin

Popular questions and responses by Justin
1. ## math

The number of Roberto's baseball cards is 3/4 the number of David's cards. If Roberto gives 1/2 of his cards to David, what will be the ratio of Roberto's cards to David's cards?

2. ## Math

Let (7,-3) be a point on the terminal side of theta. Find the exact values of sin of theta, csc of theta and cot of theta?

3. ## physics

A copper wire has a resistance of 0.425 at 20.0°C, and an iron wire has a resistance of 0.455 at the same temperature. At what temperature are their resistances equal?

4. ## physics

A 0.810 m long brass pendulum experiences a 18.0°C temperature increase. (a) Calculate the original period(s). (b) What is the change in the period(s)? (c) Find the ratio of the change in period to the original period, and calculate how long (h) a clock

5. ## Calculus

1. The graph of f ′′(x) is continuous and decreasing with an x-intercept at x = –3. Which of the following statements must be true? A. The graph of f is always concave down. B. The graph of f has an inflection point at x = –3. C. The graph of f has

6. ## economics

you find out that your aunt works for a defense manufacturing company that has several defense contracts with the government. she tells you that she works for a team that is producing a communications satelluite

7. ## Physics

Assume that a certain city consumes electrical energy at an average rate of 2.0× 10^9 W. What would be the mass change in producing enough energy to keep this city running for 21 weeks?

8. ## physics

20 kg , 30 cm diameter disk is spinning at 300 rpm. How much friction force must be applied to rim to bring the disk to a halt in 3.0s?

9. ## Geometry

Point D is on the interior of angle ABC. Use the given information to find m angle DBC. (Draw the picture.) M angle ABC = (5x +6) M angle ABD = (7x - 9) M angle DBC = (5x - 6) Answer so far: (5x + 6) + (5x - 6) = (7x - 9) 10x = 7x - 9 10 x - 7x = -9 3x =

10. ## art

The math tessellations: unit 4 1. The architectural design was created by: 1. using an organic pattern in the form of tessellation. 2. using a geometric pattern in the form a tessellation. 3. using no definite pattern and placing shapes randomly. 4. using

11. ## Information Systems

Problem #2 from page 173 Given the following business scenario, create a Crow’s Foot ERD using a specialization hierarchy if appropriate. Tiny Hospital keeps information on patients and hospital rooms. The system assigns each patient a patient ID number.

12. ## science

how many kilojoules of heat must be transferred to a 480 g aluminum pizza pan to raise its temperature from 22 degree c to 234 degree c? The specific heat of aluminum in this temperature range is 0.97 J/g degree C.

13. ## chem101

50.0ml of 0.10M HCL{aq} was added to 40.0ml of 0.10M NaOH{aq} and the mixture was stirred,then tested with a pH meter.What reading should be obtained for pH at 25.0degrees celcias?

14. ## Calculus

For Questions 1–3, use the differential equation given by dx equals xy/3, y > 0. Complete the table of values x −1 −1 −1 0 0 0 1 1 1 y 1 2 3 1 2 3 1 2 3 dy/dx ? ? ? ? ? ? ? ? ? Find the particular solution y = f(x) to the given differential

15. ## math calculus

The concentration C (in milligrams per milliliter) of a drug in a patient's bloodstream t hours after injection into muscle tissue is modeled by C = 3t/26 + t^3 Use differentials to approximate the change in the concentration when t changes from t = 1 to t

16. ## Physics

The person in the drawing is standing on crutches. Assume that the force exerted on each crutch by the ground is directed along the crutch, as the force vectors in the drawing indicate. If the coefficient of static friction between a crutch and the ground

17. ## Physics

A relativistic proton has a momentum of 1.0×10^-17 kg ∙ m/s and a rest energy of 0.15 nJ. What is the kinetic energy of this proton? (c = 3.00 × 108 m/s, mass of proton = 1.67 × 10-27 kg)

18. ## Physics

The pressure exerted by a phonograph needle on a record is surprisingly large. If the equivalent of 1.00 g is supported by a needle, the tip of which is a circle 0.200 mm in radius, what pressure is exerted on the record in N/m2?

19. ## Physics

. (a) Calculate the angular momentum of an ice skater spinning at 6.00 rev/s given his moment of inertia is 0.400 kg ⋅ m2. (b) He reduces his rate of spin (his angular velocity) by extending his arms and increasing his moment of inertia. Find the value

20. ## Chemistry

If 2.50 g of CuSO4 are dissolved in 9.4 102 mL of 0.34 M NH3, what are the concentrations of Cu(NH3)42+, NH3 and Cu2+ at equilibrium? i tried doing Cu2+ first and i did Kf=5e13= salt/cu2+ nh3+^4 and i did molesCuSO4/.94 L = .01666 M salt so then i did

21. ## physics

Four identical metallic spheres with charges of +2.2 µC, +8.2 µC, −4.6 µC, and −9.2 µC are placed on a piece of paper. The paper is lifted on all corners so that the spheres come into contact with each other simultaneously. The paper is then

22. ## Math

Serena paid \$20.20 for 36 rulers and folders. She bought 16 more folders than rulers. If each folder cost \$0.50 more than each ruler, how much did each folder cost?

23. ## physics

A 1300-kg car rolling on a horizontal surface has speed v = 65 km/h when it strikes a horizontal coiled spring and is brought to rest in a distance of 2.3 m. What is the spring stiffness constant of the spring?

24. ## Calculus

The differential equation dy/dx= -x/y I. will have a slope field with negative slopes in all quadrants II. will have a slope field with positive slopes in all quadrants III. will produce a slope field with rows of parallel tangents Choices: A. I only B. II

25. ## Calculus

Use geometry(geometric formulas) to evaluate the integral from 0 to 6 f(x) dx, for the system of equations: f(x)= 4-x for x LESS than or EQUAL to 4 and equals 2x-8 for x > 4. A. 24 B.8 C.16 D.12 I could really use some help please! Thank you!

26. ## Physics

A basketball player throws a ball at an angle of 30º above the horizontal. At what point does the magnitude of the acceleration reach a minimum?

27. ## Calculus

A biker is slowing down according to the following table of velocities: Time (secs) 0 1 2 3 4 Velocity (feet/sec) 25 20 16 12 10 Approximate the distance traveled, in feet, during these 4 seconds using 4 rectangles and a Left Riemann Sum. A. 20.75 B. 58

28. ## physics

19 cars in a circle at a boom box competition produce a 130 dB sound level at the center of the circle. What is the average sound level(dB) produced there by each, assuming interference effects can be neglected? Please someone help me to solve this

29. ## physics

How many times a minute does a boat bob up and down on ocean waves that have a wavelength of 43.0 m and a propagation speed of 5.25 m/s?

30. ## physics

Suppose a diving board with no one on it bounces up and down in a simple harmonic motion with a frequency of 3.00 Hz. The board has an effective mass of 10.0 kg. What is the frequency of the simple harmonic motion of a 62.0 kg diver on the board?

31. ## Physics

What is the final velocity of a hoop that rolls without slipping down a 5.00-m-high hill, starting from rest?

32. ## Calculus

Use the Midpoint Rule with the given value of n to approximate the integral. Round the answer to four decimal places. int_2^10 2 sqrt(x^2+5)dx text(, ) n=4

33. ## Calculus

Use geometry to evaluate the integral from 0 to 6 of the function f of x, dx for the system of equations: f(x)= 3 for x LESS than or EQUAL to 3 and equals 6-x for x > 3. A. 27 B.13.5 C.12 D.10.5 I could really use some help. Thank you!

34. ## IPC

A hailstone traveling with a velocity of 43 meters/second comes to a virtual stop 0.28 seconds after hitting water. What is the magnitude of its acceleration in the water? a. 12 meters/second2 b. 1.5 × 102 meters/second2 c. 78.6 meters/second2 d. 6.5 ×

35. ## physics

(a) What is the hot resistance of a 24 W light bulb that runs on 120 V AC? (b) If the bulb's operating temperature is 2700°C, what is its resistance at 2570°C?

36. ## Physics

Suppose you exert a force of 180 N tangential to a 0.280-m-radius 75.0-kg grindstone (a solid disk). (a)What torque is exerted? (b) What is the angular acceleration assuming negligible opposing friction? (c) What is the angular acceleration if there is an

37. ## math

a fireman stood on the middle step of a ladder, shooting water into a burning building, as the smoke lessened, he climbed up 3 steps, and continued his work, the fire got worse, so he had to go down 5 steps, later he climbed up the last 6 steps and was at

38. ## Biology

Plz i need help. Plants are green because the pigments in plants reflect green light. Blue and red light give them the most energy to power photosynthesis. You are conducting an experiment to see how different colors of light affect the growth of plants.

39. ## math

The Smiths want to buy a 9 ft. by 12 ft. carpet and center it in a 15 ft. by 20 ft. room. Can a 3 1/2 foot by 12 foot couch be placed against one of the long walls of the room without touching the carpet?

40. ## physics

An aluminum can is filled to the brim with a liquid. The can and the liquid are heated so their temperatures change by the same amount. The can’s initial volume at 8 °C is 4.8 × 10-4 m3. The coefficient of volume expansion for aluminum is 69 × 10-6

41. ## Physics

A 0.02 kg-lead bullet traveling 200 m/s strikes an armor plate and comes to a stop. If all of it's energy is converted to heat that it absorbs, what is the temperature change?

42. ## Physics

A 35-g block of ice at -14°C is dropped into a calorimeter (of negligible heat capacity) containing 400 g of water at 0°C. When the system reaches equilibrium, how much ice is left in the calorimeter? The specific heat of ice is 2090 J(kg K) and the

43. ## Physics (Force)

A power wheelbarrow has a mass of 432 kg. What force must be applied to give it an acceleration of 1.75 m/s2?

44. ## math

If Sue worked 6 3/4 hours on Monday, 4 hours on Tuesday, 7 3/4 hours on Wednesday, 8 hours on Thursday, and 5 1/2 hours on Friday, calculate her weekly wage at \$7.20 per hour.

45. ## physics

An 8 hour exposure to a sound level of 95.0 dB may cause hearing damage. What energy in joules falls on a 0.850 cm diameter eardrum so exposed? I try to use k = IAT = (1*10^-3)(0.0085^2)(8*3600)=0.00208 but answer is not correct.

46. ## geomtry

find the arc length of the minor arc withe degree of 120 and a radius of 8

47. ## math

A pilot can travel 400 miles with the wind in the same amount of time as 336 miles against the wind. Find the speed of the wind if the pilot's speed in still air is 230 miles per hour.

48. ## Physics Prob.

A 22.0 kg child plays on a swing having support ropes that are 2.00 m long. A friend pulls her back until the ropes are 45.0 ∘ from the vertical and releases her from rest. What is the potential energy for the child just as she is released, compared with

49. ## Geometry

Which of the following represents a chord but not a diameter of the circle? A. TR B. SN C. PM D. SM

50. ## Physics

A 4.0-kg mass is placed at (3.0, 4.0) m, and a 6.0-kg mass is placed at (3.0, -4.0) m. What is the moment of inertia of this system of masses about the x-axis?

51. ## calculus

find the equation of the curve for which y''=6x-4 and which passes through (1,2) and (-2,5).

52. ## math

Frank owns 300 acres of land. If he divides the land into 1/2 acre plots, how many plots will he have?

53. ## science

A science teacher tells her class that their final project requires the students to measure a specific variable and determine the velocity of a car with no more than 2.5% error. Jennifer and Johnny work hard and decide the velocity of the car is 34.87 m/s.

54. ## pre-algrebra

What is the missing coefficient x 2 4x -2x x 2 ______ x

55. ## Calculus

1. Find the domain for the particular solution to the differential equation dy/dx=3y/x, with initial condition y(1) = 1. A. x > 0 B. x < 0 C. x ≠ 0 D. All real numbers 2. Use geometry to evaluate the integral from negative 2 to 6 of f of x, dx where f of

56. ## Calculus

1. The differential equation dy/dx equals x-2/y-2 I .produces a slope field with horizontal tangents at y = 2 II. produces a slope field with vertical tangents at y = 2 III. produces a slope field with columns of parallel segments A. I only B. II only C. I

57. ## math

Rewrite the expression without using a negative exponent. -2m^-5 Simplify the answer as much as possible.

58. ## Science

Explain what Maria and craters are and how they formed.

59. ## Calculus

Finding critical numbers g(theta) = 16(theta) - 4tan(theta) I can only get the derivative of g to be g'(theta) = 16 - 4sec^2(theta). Am I supposed to move on to get sec^2(theta) = 4, then sec(theta) = 2?

60. ## math

Brendan got 31 questions correct on his social studies test and missed 9 questions. What percent did he have correct?

61. ## physics

An 8 hour exposure to a sound level of 95.0 dB may cause hearing damage. What energy in joules falls on a 0.850 cm diameter eardrum so exposed?

62. ## physics

When a pendulum with a period of 2.00000 s is moved to a new location from one where the acceleration of gravity was 9.80 m/s2, its new period becomes 1.99711 s. By how much does the acceleration of gravity differ at its new location? (m/s2)

63. ## physics

(a) What is the best coefficient of performance for a heat pump that has a hot reservoir temperature of 50.0°C and a cold reservoir temperature of -20.0°C? (b) How much heat in kilocalories would it pump into the warm environment if 3.60 multiplied by

64. ## physics

A spring has a length of 0.260 m when a 0.300 kg mass hangs from it, and a length of 0.750 m when a 1.90 kg mass hangs from it.(a) What is the force constant of the spring?(b) What is the unloaded length of the spring?

65. ## Physics

A straightforward method of finding the density of an object is to measure its mass and then measure its volume by submerging it in a graduated cylinder. What is the density of a 240-g rock that displaces 89.0 cm3 of water? (Note that the accuracy and

66. ## Physics

What is the moment of inertia of an object that rolls without slipping down a 2.00-m-high incline starting from rest, and has a final velocity of 6.00 m/s? Express the moment of inertia as a multiple of MR2, where M is the mass of the object and R is its

67. ## Physics

A golf ball rolls off a horizontal cliff with an initial speed of 12.2 m/s. The ball falls a vertical distance of 17.3 m into a lake below. (a) How much time does the ball spend in the air? (b) What is the speed v of the ball just before it strikes the

68. ## Physics

A 3.00-liter aluminum cylinder at 5.00°C is filled to the brim with gasoline at the same temperature. If the aluminum and gasoline are warmed to 52.0°C, how much gasoline spills out? [Hint: Be sure to account for the expansion of the container. Also,

69. ## math

a refrigerator is 3 ft wide, 2.5ft deep,and 6ft high. The walls and other parts other refrigerator take up to 20ft. How much cubic feet are left for food?

70. ## Pre-Algebra

solve for m 2/3m - 5 = n

71. ## Chemistry

A compound has the empirical formula CHCl. A 256 mL flask, at 373 K and 750. torr, contains 0.800 g of the gaseous compound. Give the molecular formula.

72. ## physics

What is the maximum speed with which a 1200-kg car can round a turn of radius 68 m on a flat road if the coefficient of static friction between tires and road is 0.80?

73. ## Math

I need to find the surface area and volume of a right regular hexagonal prism. The height is 10cm and the sides of its base measure 18cm. You round to the nearest hundredth.

74. ## Calculus

1. The function is continuous on the interval [10, 20] with some of its values given in the table above. Estimate the average value of the function with a Left Hand Sum Approximation, using the intervals between those given points. x 10 12 15 19 20 f(x)

75. ## Calculus

The function f is continuous on the interval [3, 13] with selected values of x and f(x) given in the table below. Use the data in the table to approximate f ′(3.5). x 3 4 7 10 13 f(x) 2 8 10 12 22 Please HELPP! Thank you

76. ## Calculus

The base of a solid is the circle x^2 + y^2 = 9. Cross sections of the solid perpendicular to the x-axis are squares. What is the volume, in cubic units, of the solid? A. 18 B. 36 C. 72 D. 144 Please help. Thank you in advance.

77. ## Math

Dan has twice as many stickers as Cam does. If Dan gives Cam 15 of his stickers he will still have 22 more than Cam. How many stickers does each boy have?

78. ## Physics

A car travelling at 30m/s overcomes a frictional resistance of 100N while moving. Calculate the power developed by the engine.[1hp=0.75]

79. ## Math

1. Graph the points A ( -5,0) B ( -4, 3) and C ( 0, -4) A B C D 2. Identify the quadrant in which (3, -6) lies A II B IV C I D III 3. Determine which ordered pair is a solution of y = 2x - 3 A ( -2, 7) B ( 0, 3) C ( -4, -11 D ( 5, -7 5. Graph the linear

80. ## Geometry

A 20 meter long cable is used to support a telephone pole, holding it perpendicular to the ground. If the cable forms a 60 degree angle with the ground, how high up the pole should the cable be attached?

81. ## Ray Optics

Hi, this is about thin film interference in ray optics. My book presents two similar problems, but somehow uses different paths for the same variable. I'll list out the given variables: --Problem A-- n1 < nf > n2, delta phase is therefore lambda over two.

82. ## pre algebra

2.5x10^-5 equals what?

83. ## Chemistry

Enthalpy I'm given that the heat of reaction for the combustion of ethane is -1560kJ/mol. I need to figure out how much heat is produced from 18g of ethane. 2 C2H6 + 7 O2 --> 4 CO2 + 6 H2O Okay so I'm rough on Thermo right now, so I gave it my best shot.

84. ## Math

My numerator is less than my denominator.I am more than 1/2. What fractions can Ibe

85. ## calculus

a particle starts from rest and moves along a straight line with an acceleration equal to 24-15√t where distance and time are measured in terms of feet and seconds respectively. with what acceleration will the particle return to the starting point?

86. ## M ath

Sally has a sum of \$26000 that she invests at 9% compounded monthly. What equal monthly payments can she receive over a period of a) 9 years? b) 7 years?

87. ## FRACTION CONCEPTS

I am a fraction whose numerator and denominator are both prime numbers less than 20. if you were to increase each term by 1, I would be equivalent to 1/2. what fraction am I?

88. ## chemistry

Are my answers correct? Identify each energy exchange as primarily heat or work and determine weather the sign of ΔE is positive or negative for the system. A. A rolling billiard ball collides with another billiard ball. The first ball (system) stops

89. ## math

An alloy of copper is 10% copper and weighs 25 pounds. A second alloy is 18% copper. How much (to the nearest tenth lb.) of the second alloy must be added to the first alloy to get a 13% mixture.

90. ## math

If the angle of declination is known, a surveyor would use_______ to find the length x. The cosine of a 50° angle is_______ this represents the value created when length x is divided by 90 feet. If the angle of declination changed to 60°, the cosine

91. ## English

In "Paul's Case," members of the faculty don't like Paul's carnation because they think A. it doesn't match his other clothing. B. it suggests that he's not taking things seriously. C. it's the mark of an early death. D. it's effeminate for a man to wear a

92. ## Phyics

One of the concrete pillars that supports a house is 1.9 m tall and has a radius of 0.55 m. The density of concrete is about 2.2 x 103 kg/m3. Find the weight of this pillar in pounds (1 N = 0.2248 lb).

93. ## Chemistry

which is more accurate direct weighting or weighing by difference?

94. ## physics

Assuming 95.0% efficiency for the conversion of electrical power by the motor, what current must the 12.0 V batteries of a 740 kg electric car be able to supply: (a) To accelerate from rest to 25.0 m/s in 1.00 min? (b) To climb a 200 m high hill in 2.00

95. ## physics

If an electron travels 0.150 m from an electron gun to a TV screen in 19.0 ns, what voltage was used to accelerate it? (Note that the voltage you obtain here is lower than actually used in TVs to avoid the necessity of relativistic corrections.)

96. ## physics

A 45.0 g ball of copper has a net charge of 1.5 µC. What fraction of the copper's electrons have been removed? (Each copper atom has 29 protons, and copper has an atomic mass of 63.5.)

97. ## Chemistry

Given the reaction: Ni (s) + 4 CO (g)  Ni(CO)4 (g) E = –154 kJ, how many kilograms of CO are required for this reaction to release 756 kJ of energy?

98. ## physics

An 8 hour exposure to a sound level of 95.0 dB may cause hearing damage. What energy in joules falls on a 0.850 cm diameter eardrum so exposed?