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Compound Body Problems. Required Steps. Identify the variable(s) the problem asks you to calculate. Draw FORCE DIAGRAM (or two FBD’s, or three FBD’s, or…) Write the “Compound Body Version” 2 nd Law (or the expanded 2 nd Law formula s, one for each FBD)
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Required Steps • Identify the variable(s) the problem asks you to calculate. • Draw FORCE DIAGRAM (or two FBD’s, or three FBD’s, or…) • Write the “Compound Body Version” 2nd Law (or the expanded 2nd Law formulas, one for each FBD) • Substitute given or computed values into the formula • Solve for acceleration • Make FBD for on part, write expanded 2nd law, sub and solve for internal (to the system) force
Ex1: Atwood Device • Determine the acceleration of the masses and the tension in the string. Assume the pulley is massless And frictionless. 1 2 10.0 kg 3.33 kg
Ex 2: Modified Atwood Device • The block on the table is 5m, and the hanging block is m. Assuming no friction and a massless pulley, compute the acceleration of the system, and the tension in the string. 2 1
Ex 3 (String & Incline & Pulley, Oh My!) • Determine the acceleration of the system, and tension in the string. The slope is 30.0° and the masses are 1.00kg and 3.00kg. (assume no friction and massless pulley) 2 2 1
Ex 3 • Determine the minimum coefficient of static friction if the blocks remain at rest. The slope is 30.0° and the two masses are 1.00kg and 3.00kg.
Ex 3 Cont. • Determine the coefficient of kinetic friction if the blocks slide at a constant speed. The slope is 30.0° and the two masses are 1.00kg and 3.00kg.