A 2.0-kg silverware drawer does not slide readily. The owner gradually pulls with more and more force, and when the applied force reaches 9.0 N, the drawer suddenly opens, throwing all the utensils to the floor. What is the coefficient of static friction between the drawer and the cabinet?
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This is Giancoli Answers with Mr. Dychko. At just the moment when this drawer begins to slide, we have the pulling force equaling the friction force. And, I mean, the pulling force would be just ever so slightly bigger than the friction force I suppose. But we're just at that moment when they're equal is the question here. So, the friction force equals static friction coefficient times the normal force. And the normal force, since it's the only force upwards, has to equal the total force downwards which is mg. And so, we substitute mg in for the normal force. And so, we have that the pulling force in other words, equals muS times mg. And so, we can set those two equal to each other and then divide both sides by mg. And then we get that coefficient of static friction is the pulling force divided by mass times gravitational field strength. So, is 9 Newtons divided by 2 kilograms times 9.8 Newtons per kilogram which is coefficient of static friction of 0.46.
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