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    Electro-static energy

    Homework Statement hello I have a question,it's not homework related..I know the electro-static energy of a sphere is:(3/5)kQ/R I tried to calculate it today using the expression: U = 1/2 * integral (phi * rho dV) where: phi is the potential, rho is charge density(uniform), dV is the...
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    Center of mass

    Homework Statement figure attached: Uniform beam with mass M,is placed horizontally,pivoted about it's center on the beam there are two small masses m1 and m2,connected by a spring,the system is in equilibrium,and at t=0 the spring is cut,and m1 and m2 slide on the beam.(their speed is not...
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    Rigid Body: bullet and a rod

    Homework Statement a rod with mass 'M' and length 'L' is pivoted about a frictionless axle through it's end .a bullet with mass 'm' and speed 'v' is shot and sticks to the rod a distance 'a' from the axle. I need to find the LINEAR momentum of the system just after the hit. Homework...
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    Circular motion

    Homework Statement A figure is attached. The symmetric system consists of 4 massless rodes with length 'L',the purple thing is a spring(the spring constant is k),when the system is at rest theta=45 deg. the system starts to rotate with angular speed 'w',the rodes are pushing on the...
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    Potential Energy

    Homework Statement A figure is attached. A string with length L connects two beads with masses M1,M2. what is the equilibrium point?(in terms of the angle theta,as in the figure) The Attempt at a Solution well I know that I need to find the potential energy as a function of theta,and then...
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    Potential Energy

    Homework Statement Particle x is bounded to another particle P by force which is dependent on their distance 'r',the potential derived from this force is: U(r) = a/r^3 - b/r^2 a,b>0 (a)how much energy is required to seperate the particles?. (b)suppose particle x has kinetic energy...
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    Block on inclined plane

    hello,i'm having some trouble with this problem. a block with mass m,rests on a frictionless plane,inclined at angle alpha relative to the horizon. what is the acceleration 'a' of the plane,if we dont want the block to slide down the plane? here's what i've tried: the x axis will be parallel...
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    Circular motion

    hello planet earth is orbiting the sun with angular frequency w,and radius r1. the moon,which is orbiting the earth with the same angular frequency w(in planet earth's frame) and radius r2. and together they are orbiting the sun. now I need to describe the position vector of the moon as a...
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    Linear motion

    hello I'm having some trouble with the following problem: train B leaves point A at 8am to point B located 30 km straight a head. the train has constant acceleration a=0.05 m/sec^2 now train B leaves point B 5 minutes before train A gets there,what is the acceleration of train B in...
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    Classical mechanics: centripetal acceleration

    I need some help with centripetal acceleration. why when an object is whirling in a vertical circle,it must have a centripetal acceleration larger than 'g' in order for it to get to the top of the circle? what if I give it just enough speed to get to the top(so when it gets to the top,it's...
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    Kinematics - Archer shooting arrow at apple

    Hello all.:smile: First I want to say that i'm really new to physics,started like a week ago. and that this is NOT homework(i'm studying by myself) An archer shoots an arrow with a velocity of 45.0 m/s at an angle of 50.0° with the horizontal. An assistant standing on the level ground...
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