1) A 0.075 kg arrow is fired horizontally. The bow string exerts anaverage force

Question

1) A 0.075 kg arrow is fired horizontally. The bow string exerts anaverage force of 65N on the arrow over a distance of 0.90m withwhat speed does the arrow leave the bow?

2) A 100kg crate is being pulled across a horizontal floor by aforce P that makes an angle of 30 degrees above the horizontal. Thecoefficient of kinetic friction is 0.200. What should be themagnitude of P so that the net work done by it and kineticfrictional force is zero?

darn, i've tried to answer these questions... and i'm startin toget crazy =))
can someone help? :) thanks a bunch!~

Explanation / Answer

Ans. 1> From conservation of energy,          0.5*m*v^2=force*displacement          0.5*0.075*v^2=65*0.90=58.5          v=39.50 m/s   [Ans.]        2>net workdone=0           work done due to applied force= work done due to frictionalforce              p*3/2=0.200*(100-0.5*p)               p=20.703 kg.    [Ans.]

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