COReept questions 1. (20 points, 5 points each): (a) A professor holds an eraser

Question

COReept questions 1. (20 points, 5 points each): (a) A professor holds an eraser against a vertical chalkboard by pushing horizontally on it. She pushes with a friction force that is much greater than is required to hold the eraser. In which of the cases does the force of friction exerted by the board on the eraser increases? (i) She pushes with slightly greater force. (ii) She pushes so her force is slightly downward but has the same magnitude. ) She pushes so her force is slightly upward but has the same magnitude. (b) An airplane is flying in a horizontal circle at constant velocity. To maintain the uniform circular motion the airplane is banked as show, with the following forces acting on the plane; thrust force T, drag force D, vertical lift force L, horizontal lift force Fe, and gravitational force W. Express symbolically the work done by each of these forces after the plane has completed a fully circle of radius R. L. IW gravity (c) A block is attached to a compressed horizontal spring resting on a surface with friction. If the compressed spring and block are released from rest, about where does the block achieve maximum velocity? How do the values of the kinetic coefficient of friction and spring constant affect this location of maximum velocity? (d) Two balls of mass m and m2 collide elastically in a head-on 1D collision on a frictionless surface. The ball with mass m, has an initial velocity of v,. What relative values of v2, m, and m2 will lead to the greatest transfer of kinetic energy from one ball to the other?

Explanation / Answer

For part a
(i) no increase, as the max friction force can be in this case the total downward force on it which is in this case its weight, the weight is already balanced by the earlier friction force
(ii) In this case she is increasing the total downward force as she directs her force in slightly downward direction so this componant adds to the weight and increases the total friction force
(iii) It is opposite of case 2, so slight decrease

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