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  1. K

    Ball thrown upward and another is dropped

    Draw a picture, with the applied forces.
  2. K

    Force and Motion (net force)

    The 'net force' in the statements below is the sum of ALL forces acting on the body. During the collision of a car with a locomotive, the locomotive exerts an equal size force on the car as the car exerts on the locomotive. False If an object's speed does not change, no net force is...
  3. K

    Electric field (easy at least I thought so)

    The electric field strength 5.0 cm from a very long charged wire is 2000 N/C. What is the electric field strength 10.0 cm from the wire? Okay I thought that since the radius is double what it was before using the equation: E= K*q*(r head)/(r^2) I said that it decreases 1/4 and becomes...
  4. K

    Carnot Refrigerator coefficient of performance

    A Carnot refrigerator operating between -10.0 C and 40.0 C extracts heat from the cold reservoir at the rate 300 J/s. What are (a) the coefficient of performance of this refrigerator, (b) the rate at which work is done on the refrigerator and (c) the rate at which heat is exhausted to the hot...
  5. K

    Heat needed to change temperature of hydrogen gas

    nevermind monatomic at that temp
  6. K

    Heat needed to change temperature of hydrogen gas

    Oh! But When I do that I get .65/2 = .325 .325*20.775*50 = 337.6 which is still wrong
  7. K

    An Air Conditioner: Refrigerator or Heat Pump?

    Air conditioners operate on the same principle as refrigerators. Consider an air conditioner that has 7.00 kg of refrigerant flowing through its circuit each cycle. The refrigerant enters the evaporator coils in phase equilibrium, with 54.0% of its mass as liquid and the rest as vapor. It flows...
  8. K

    Heat needed to change temperature of hydrogen gas

    But i also calculated it for monotomic too....
  9. K

    Heat needed to change temperature of hydrogen gas

    A rigid container holds 0.650 of hydrogen gas. How much heat is needed to change the temperature of the gas from 50 K to 100 K? All right I know this is easy but for some reason I can't get the right answer what i have been doing is using the equation Q=nC_v(T_f-T_i) Hydrogen gas is 1 g/mol...
  10. K

    Roling vs Sliding Down an incline

    Think about 2 objects (one rolling one sliding) down an incline. In terms of energy, see what you came up with and how they differ...be verbose! All right I know that the rolling object would go down the incline faster and...i'm not sure but I think...the sliding one would gather the most...
  11. K

    Oscillations of air-track glider

    A 160 g air-track glider is attached to a spring with spring constant 4.40 N/m. The damping constant due to air resistance is 2.40×10−2 kg/s. The glider is pulled out 23.0 cm from equilibrium and released. How many oscillations will it make during the time in which the amplitude decays to...
  12. K

    Pressure pn a Dam

    As the reservoir behind a dam is filled with water, the pressure that the water exerts on the dam increases. Eventually, the force on the dam becomes substantial, and it could cause the dam to collapse. There are two significant issues to be considered: First, the base of the dam should be able...
  13. K

    Torque? Rotation it has the Word Pivot

    Torque? Rotation it has the Word Pivot.... A forearm can be modeled as a 2.50 kg, 32-cm-long "beam" that pivots at the elbow and is supported by the biceps. http://session.masteringphysics.com/problemAsset/1001007/10/knight_Figure_13_58.jpg How much force must the biceps exert to hold a 430...
  14. K

    Static Equilibrium of the Arm

    You are able to hold out your arm in an outstretched horizontal position because of the action of the deltoid muscle. Assume the humerus bone has a mass m=3.6, length L=0.66 and its center of mass is a distance L1=0.33 from the scapula. (For this problem ignore the rest of the arm.) The deltoid...
  15. K

    Newton's Theory of Gravity and impact speed

    A 1.0 kg object is released from rest 500 km above the earth. A. What is its impact speed as it hits the ground? Ignore air resistance B. What would the impact speed be if the earth were flat? I don't know how to start this. I said that v=sqrt(2G*M_e*m/(R_e+300))= 1.33*10^9 but that is...
  16. K

    Work? maybe just kinematic (please help! I don't even know what it is!)

    Work?....maybe just kinematic...(please help! I don't even know what it is!) The spring shown in the figure is compressed 50 cm and used to launch a 100 kg physics student. The track is frictionless until it starts up the incline. The student's coefficient of kinetic friction on the 30 degree...
  17. K

    Deriving integral=arctan

    no he actually wants us to plow thorugh the intregal using subsitution and stuff and then somehow end up at the answer
  18. K

    Deriving integral=arctan

    Yeah this one is good.... Derive the following: int(1/(x^2 + a^2)dx = 1/a*arctan(x/a) + C any idea how I would derive this thing? Cause I'm totally lost....
  19. K

    WORK by Constant Force Argh help

    http://session.masteringphysics.com/problemAsset/1000845/7/knight_Figure_11_47.jpg This is the figure but I was told that it didn't matter since all that matters is hight when there is no friction
  20. K

    WORK by Constant Force Argh help

    WORK by Constant Force....Argh....help A freight company uses a compressed spring to shoot 1.80 kg packages up a 1.0-m-high frictionless ramp into a truck, as the figure shows. The spring constant is 337 N/m and the spring is compressed 34.0 cm. A) What is the speed of the package when it...
  21. K

    Newton's 2nd law with an incline plane (I think help0

    Newton's 2nd law with an incline plane (I think....help0 The 1930 kg cable car shown in the figure descends a 200-m-high hill. In addition to its brakes, the cable car controls its speed by pulling an 1830 kg counterweight up the other side of the hill. The rolling friction of both the cable...
  22. K

    Package by Air (project time motion)

    never mind I found it out :) i am really stupid....
  23. K

    Package by Air (project time motion)

    I found part A D=(v0-v1)*sgrt(2h/g)
  24. K

    Package by Air (project time motion)

    A relief airplane is delivering a food package to a group of people stranded on a very small island. The island is too small for the plane to land on and the only way to deliver the package is by dropping it. The airplane flies horizontally with constant speed at an altitude . The package is...
  25. K

    Delivering a Package by Air (Project Time Motion) help

    Delivering a Package by Air (Project Time Motion)......help A relief airplane is delivering a food package to a group of people stranded on a very small island. The island is too small for the plane to land on and the only way to deliver the package is by dropping it. The airplane flies...
  26. K

    Projectile Motion Help

    A projectile is fired from ground level at time 0, at an angle theta with respect to the horizontal. It has an initial speed v0. In this problem we are assuming that the ground is level. Find , the maximum height attained by the projectile, okay it is just asking for the equation I know I need...
  27. K

    Inertial frame of reference help

    awesome it worked thank i should of thought about it acting on them from angles
  28. K

    Inertial frame of reference help

    there is more than 3 it told me
  29. K

    Inertial frame of reference help

    is it d? because that is what i tried and it was wrong
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