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More Friction Problems... 1. An applied force of 20 N accelerates a 9 kg wagon at 2 m/s2 along the sidewalk. A) What is the net force? (HINT: Use Newton’s 2nd Law) Given Unknown Equation Substitute Solve B) How large is the frictional force? (HINT: A free body diagram might help) Given Unknown Equation Substitute Solve C) What is the coefficient of friction? (HINT: Use mass of wagon to find FW) Given Unknown Equation Substitute Solve Substitute Solve 2. A 2 kg brick has a sliding coefficient of friction of 0.38. A) What is the magnitude of the normal force? (HINT: Find FW first) Given Unknown Equation B) What force must be applied to the brick for it to move at a constant velocity? (HINT: Ffk = FP) Given Unknown Equation Substitute Solve 3. The forces required to move an 8.24 kg metal cube are measured: 42.8 N are required to start motion and 32.5 N are necessary to keep it moving at constant velocity. A) What is the magnitude of the normal force? Given Unknown Equation Substitute Solve B) What is the coefficient of static friction? (HINT: One of the applied forces given = Ffs) Given Unknown Equation Substitute Solve C) What is the coefficient of kinetic friction? (HINT: One of the applied forces given = Ffk) Given Unknown Equation Substitute Solve
