The block, A, with mass of 3m slides down an incline with slope at a constant speed. The top plank, B, with mass m is attached to the wall by a massless cord. The coefficient of kinetic friction between the block and the plank is μ. The coefficient of kinetic friction between the block and the incline is also μ. Required:
a. Determine the coefficient of kinetic friction μ
b. Determine the tension in the cord.

Aballet student who learns with the of his instructor is demonstrating learning.

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Four point charges each having charge q are located at the corners of a square having sides of length a. find symbolic expressions for the following. (a) the total electric potential at the center of the square due to the four charges (use any variable or symbol stated above along with the following as necessary: ke.) vtotal= (b) the work required to bring a fifth charge p from infinity to the center of the square (use any variable or symbol stated above along with the following as necessary: w=