Recent content by shenwei1988

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    Entropy of a system can never decrease

    heat! so hard. true or false 1.The entropy of a system can never decrease 2.All Carnot engines are reversible 3.It is impossible have a net transfer of heat from a cold reservoir to a warm reservoir 4.A refrigerator lowers the entropy of the volume inside 5.If the temperature...
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    Find the coefficient of static friction

    F=mg=25x9.8 for question 1.) f=Fu ---> 165=25x9.8xu find u , u is the coefficient of static friction between the chair and the floor. try to do 2 by yourself
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    Find the coefficient of static friction

    F=mg f=mgu 165N is the static friction force 127N is the kinetic friction force simply put in the number f(s)=F*u
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    Total force by molasses on inside of tank

    by the way, i am sure if we need to consider the air pressure or not.
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    Total force by molasses on inside of tank

    Homework Statement On January 15, 1919, a cylindrical tank of molasses ruptured, and poured out over the streets of Boston in a 9 m deep stream. Pedestrians and horses were killed, and buildings were knocked down. Suppose the tank was 87.7 m high and 3.37 m diameter, and it was full of...
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    Solving Fluid Problem: Help with Planet X Orbit Period

    thanks a lot, the hint you gave is so helpful. i got it right.
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    Solving Fluid Problem: Help with Planet X Orbit Period

    using Newton's law of gravity, T^2= (4π^2*r^3)/GM volume of sphere is V=4/3πr^3 ρ=M/V put in Newton's law of gravity, T^2=3πV/GM T^2=3π/Gρ
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    Solving Fluid Problem: Help with Planet X Orbit Period

    my professor gave us this problem on the homework assignment about Fluid. Planet X is a sphere made entirely of the mythical metal exoferrum, which has density 2810 kg/m3. What is the period of orbit for a satellite in circular orbit just above the surface of Planet X? (That's right: I did...
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    Rotational Energy of 3 Point Masses along a Rigid Rod

    Three point masses lie along a rigid, massless rod of length L = 5.61 m : - Two particles, both of mass m = 2.1 kg, lie on opposite ends of the rod. - Mass M = 7.29 kg is in the center of the rod. Assume the rod lies along the x-axis, and rotates about the y-axis. about a point 1.28 m...
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    Calculating Center of Mass: Rowboat with Kids | Find x Distance

    When empty, a 166 kg rowboat is symmetrical. A boy of mass 70.5 kg sits 2.1 m from the center of mass of the rowboat toward the front of the boat, and a girl of mass 68.8 kg sits 2.38 m from the center of mass of the rowboat toward the rear of the boat. Find x, distance from center mass of the...
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    What determines the net work on a hockey puck in circular motion?

    A hockey puck of mass m sits on a frictionless, horizontal table tied to a string of length L. The puck starts at rest, and accelerates to some speed v moving in a horizontal circle of radius L. The net work done on the hockey puck,depend on what? L,m,or r?? i forgot the formula for the...
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    Work and Kinetic Energy: Calculating Work and Speed with Varying Force

    not, i put the value of x. and get the force, then use the force * distance.w=(6.68*2.78^2+1.56)*2.78
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    Work and Kinetic Energy: Calculating Work and Speed with Varying Force

    The magnitude of a certain one-dimensional force varies according to: F = 6.68x^2 + 1.56 where x is the displacement from the origin in meters, and F is the force in Newtons. At t = 0, a 677 g mass is at the origin moving in the positive x-direction at speed 8.46 m/s when this force begins...
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    Calculating Work and Kinetic Energy in a Vertical Helicopter Lift

    yeah, i forgot to add the force of helicopter. thank you man!
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