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    Help! Electricity and work

    Two identical point charges of q = +1.25 x 10-8 C are separated by a distance of 1.10 m. What is the minimum amount of work required by an external force to move them closer together so that they are only 0.60 m apart? I have no idea how to do this. I tried using -q(Vb-Va), but that got me...
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    A few questions about water pressure, temp, and sound

    OK. I have done most of them correctly on my own, I need 2 checked and help with one: Check: A sound source emits sounds of frequency 210 Hz that travel through still air at 340 m/s. The source moves away from the stationary listener at 80 m/s. Find the wavelength of the sound waves...
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    Need help with 2 problems

    1.A 110 kg scaffold is 6.8 m long. It is hanging with two wires, one from each end. A 520 kg box sits 2 m from the left end. What is the tension in the left wire?(g = 9.8 m/s2) For this one I tried using: 6.8 *t=460*9.8*4.8+110*9.8*6.8/2 and solving for t, but I for some reaosn get...