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# Lecture2 - Fulcrum The point or support on which a lever...

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Fulcrum The point or support on which a lever pivots Levers can linearly increase mechanical force by adjusting the fulcrum Exploiting this law of physics allows levers to lift heavy objects with substantially less force

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Fulcrum Problem Determine the movement of the platform (clockwise or counter clockwise), if: f 1 = 10N, f 2 = 30N, f 3 = 5N, f 4 = 15N and d 1 = 2m, d 2 = d 3 = 1m, d 4 = 4m. d 1 f 1 + d 2 f 2 >or< d 3 f 3 + d 4 f 4 (2m)(10N)+(1m)(30N) = 50N < (1m)(5N)+(4m)(15N) = 65N Clockwise How far from the fulcrum must d 4 be in order for the platform to be in equilibrium? For: d 1 f 1 + d 2 f 2 = d 3 f 3 + d 4 f 4 d 4 = 3m
Tension: the force of strain that is placed on a rope or cable that results from two or more forces being applied to the rope or cable in opposite directions Pulley: a nearly rotationally frictionless wheel with a groove along its edge, for holding a rope or cable and allowing for the redirection of a pulling force or tension 1) The body that is suspended by a rope in the figure has a weight of 75N. Is T equal to, greater than or less than 75N when the body is moving downward at... (a) increasing speed (a) greater than 1. equal to 2. less than (b) decreasing speed 1. greater than 2. less than 3. equal to Pulleys and Tension

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P Q L Basic Tension Problems Block 1 = 2kg, Block 2 = 3kg and Block 3 = 5kg are connected to each other with light strings placed on a smooth frictionless surface. If the system be pulled with a force F from the side of lighter mass resulting in an acceleration of 1ms -2 . Calculate the tensions, T 1 and T 2 . For T 1 , total effective mass is mass of block 2 + mass of block 3 and acceleration applied is 1ms -2 therefore T 1 = (3kg +5kg)(1ms -2 ) = 8 N, for T 2 = (5kg)(1ms -2 ) = 5N A 1kg box M is suspended by a rope from a rigid support at a point P. Another rope is tied to a point Q, and it is pulled horizontally with a force, F = 5N. The rope between points P-Q makes angle A with the vertical. What is the tension between P-Q? An imaginary right triangle PLQ, is drawn with a vertical line from point P and a horizontal line from point Q. If the lengths of the triangle (PQ, PL, and LQ) are substituted for force magnitudes: PL = mg = 1kg X 10m/s 2 = 10N, LQ = F = 5N, and PQ = Tension. If the point Q is in equilibrium due to these three forces then: , PQ = PL/CosA = LQ/SinA = sqrt[(10N) 2 +(5N) 2 ],
3/20/2011 What is the Tension between M2 & M3?

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3/20/2011 Tension Pulley Problems Masses M 1 and M 2 are attached to the ends of the string which passes over a pulley attached to the top of a frictionless inclined plane. If M 1 = 10kg, M 2 = 5kg and A = 30 o , what is the tension in the string? Tension 1 = (F M1 )(SinA) = (10kg)(10m/s 2 )(0.50) = 50N Tension 2 = (F M2 ) = (5kg)(10m/s 2 ) = 50N The downward forces are equal and in equilibrium, thus the tension is equal to one of the forces or 50N Masses M 1 = 3kg and M 2 = 1kg are attached with the string passing over a fixed and frictionless pulley, what is the acceleration a? What is the tension between M
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