# HW12 - Precarious Lunch A uniform steel beam of length and...

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Precarious Lunch A uniform steel beam of length and mass is bolted to the side of a building. The beam is supported by a steel cable attached to the end of the beam at an angle , as shown. The wall exerts an unknown force, , on the beam. A workman of mass sits eating lunch a distance from the building. A. Find , the tension in the cable. Remember to account for all the forces in the problem. Express your answer in terms of , , , , , and , the magnitude of the acceleration due to gravity. = g*(m_1*L/2+m_2*d)/(L*sin(theta)) B. Find , the x-component of the force exerted by the wall on the beam ( ), using the axis shown. Remember to pay attention to the direction that the wall exerts the force. Express your answer in terms of and other given quantities. = -T*cos(theta) C. Find , the y-component of force that the wall exerts on the beam ( ), using the axis shown. Remember to pay attention to the direction that the wall exerts the force. Express your answer in terms of , , , , and . = -sin(theta)*T+m_1*g+m_2*g [ Print ] Sliding Dresser Sam is trying to move a dresser of mass and dimensions of length and height by pushing it with a horizontal force applied at a height above the floor.

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The coefficient of kinetic friction between the dresser and the floor is and is the magnitude of the acceleration due to gravity. The ground exerts upward normal forces of magnitudes and at the two ends of the dresser. Note that this problem is two dimensional. A. If the dresser is sliding with constant velocity, find , the magnitude of the force that Sam applies. Express the force in terms of , , and . = mu_k*m*g B. Find the magnitude of the normal force . Assume that the legs are separated by a distance , as shown in the figure. Express this normal force in terms of , , , , and . = m*g/2-mu_k*m*g*h/L C. Find the magnitude of the normal force . Assume that the legs are separated by a distance , as shown in the figure. Answer in terms of , , , , and . = m*g/2+mu_k*m*g*h/L D. Find , the maximum height at which Sam can push the dresser without causing it to topple over. Express your answer for the maximum height in terms and . = L/(2*mu_k)
A Person Standing on a Leaning Ladder A uniform ladder with mass and length rests against a smooth wall. A do-it-yourself enthusiast of mass stands on the ladder a distance from the bottom (measured along the ladder). The ladder makes an angle with the ground. There is no friction between the wall and the ladder, but there is a frictional force of magnitude between the floor and the ladder. is the magnitude of the normal force exerted by the wall on the ladder, and is the magnitude of the normal force exerted by the ground on the ladder. Throughout the problem, consider counterclockwise torques to be positive. None of your answers should involve (i.e., simplify your trig functions). A.

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## This note was uploaded on 12/06/2009 for the course PHYS 270 taught by Professor Wilfredlee during the Spring '09 term at École Normale Supérieure.

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HW12 - Precarious Lunch A uniform steel beam of length and...

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