1. A block of mass 2.00kg is pulled up a rough incline. The pulling force is 60.
ID: 1453592 • Letter: 1
Question
1. A block of mass 2.00kg is pulled up a rough incline. The pulling force is 60.0 N parallel to the incline, which makes an angle of 60 degrees with the horizontal. The coefficient of kinetic friction is 0.300, and the block is pulled 6.00m.
(a) Determine the increase in internal energy of the block-incline system owing to friction.
(b) determine the change in kinetic energy of the block.
2. A block moves through a circular path on a horizontal surface. The radius of the circle is 3.0m. The kinetic friction between the block and the surface us 5.0N. for the system consisting of the block and the surface, determine the change in the total energy of the system when the block travels one complete circle and returns to its starting point.
Explanation / Answer
1a) frictional force is fk = mu_k*m*g*cos(60) = 0.3*2*9.81*cos(60) = 2.94 N
work done by the frictional force = change in internal energy = fk*S = 2.94*6 = 17.64 J
b) Work done by the (frictional force + Pulling Force + gravitational force) = change in KE
-17.64-(m*g*sin(60)*S) +(F*S*cos(0)) = change in kE
change in KE = -17.64-(2*9.81*sin(60)*6) +(60*6*cos(0)) = 240.4 J
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2) change in total energy is f*S = 5*2*pi*r = 5*2*3.142*3 = 94.26 J
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