110-kg motorcycle and rider are traveling at 20 m/s. the rider notices a wreck ahead, applies the brakes, and manages to stop the car in 12 meters. using work-energy, find the force of friction used to stop the car. (pick the answer closest to the true value.)

a. 37,500 newtons
b. 3,375 newtons
c. 337 newtons
d. 450 newtons
e. 2,250 newtons

Acommon procedure for measuring the velocity of an airstream involves the insertion of an electrically heated wire (called a hot-wire anemometer) into the airflow, with the axis of the wire oriented perpendicular to the flow direction. the electrical energy dissipated in the wire is assumed to be transferred to the air by forced convection. hence, for a prescribed electrical power, the temperature of the wire depends on the convection coefficient, which, in turn, depends on the velocity of the air. consider a wire of length l = 20 mm and diameter d = 0.5 mm, for which a calibration of the form v = 6.25 ă— 10â’5 h2 has been determined. the velocity v and the convection coefficient h have units of m/s and w/m2 â‹… k, respectively. in an application involving air at a temperature of tâž = 25â°c, the surface temperature of the anemometer is maintained at ts = 75â°c with a voltage drop of 5 v and an electric current of 0.1 a. what is the velocity of the air?