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A 24kg block resting on a floor has a rope tied to its top. The maximum tension the rope can withstand without breaking is 310N. The minimum time in which the block can be lifted a vertical distance of 4.6m by pulling on the rope is

a) 1.2s b) 1.3s c) 1.7s d) 2.3s Solution: c) 1.7s Explanation: \(\begin{array}{l}T=m(g+a)\end{array} \) \(\begin{array}{l}a=\frac{T}{m}-g\end{array} \) Since \(\begin{array}{l}s=ut+\frac{1}{2}at^{2}\end{array} \) t=0 \(\begin{array}{l}t=\sqrt{\frac{2s}{a}}\end{array}... View Article

Two long parallel wires are separated by a distance of 2.50 cm. The force per unit length that each wire exerts on the other is 4.00xx10^-5 N/m, and the wires repel each other. The current in one wire is 0.600A. a. What is the current in the second wire? b. Are the two currents in the same direction or in opposite directions?

Solution: a) The current in the second wire is given by: \(\begin{array}{l}\frac{df}{dt}=\mu . \frac{i_{1}*i_{2}}{2\pi r}\end{array} \) \(\begin{array}{l}\frac{4*10^{-5}}{1}= \frac{2*10^{-7}*0.06*i_{2}}{2.5*0.01}\end{array} \) \(\begin{array}{l}i_{2}... View Article