quiz3v1sol

quiz3v1sol - Ph 111 NAME_RWB Quiz 3 Histogram Ph 111.01 Fal...

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Ph 111 NAME ____RWB October 10, 2008 Quiz 3 Solutions Please use the value of 9.8 m/s 2 for the acceleration of gravity, and give your numerical answers to at least three significant figures. A crate with a mass of m = 10 kg is sliding at a constant speed v 1 along a frictionless horizontal table, when it encounters a friction patch, with coefficient of kinetic friction μ k = 0.4 . After the crate has slid for a distance d = 8 m, its speed is v 2 = 11 m/s. Histogram, Quiz 3 0 10 20 30 B i n01234567891 0 Bin Frequency Ph 111.01, Fal l 2008. 110 peopl e; aver age = 5.3/ 10 C or better (a) Find the work done by the normal force over the distance d . The normal force is perpendicular to the displacement - so there is no work done. 0.00 J (b) Find the work done by friction over the distance d . The frictional force is ( )( )( ) 2 0.4 10 kg 9.8 m/s 39.2 N fN m g μμ == = = The work done is negative, given by -313.6 J () ( ) N 8 m 313.6 J = nc - - 39.2 Wf d (c) Find the speed v 1 of the crate when it first encounters the friction patch.
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