Swapnil checks his heart rate to see if he is working hard enough to qualify for a "vigorous intensity" workout according to the CDC. Which heart rate reading will let him know that he has reached this goal? A.

50 percent of his maximum heart rate

B.

60 percent of his maximum heart rate

C.

70 percent of his maximum heart rate

D.

80 percent of his maximum heart rate

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Friction force is equal to the net force of the car.             fn                           |ff< ·                       |                     fgfg and fn cancel out.55 km/h is 15.2778 m/s. this is the initial velocityfinal velocity is 0 m/sfind acceleration using kinematic equationv² = v₀² + 2adsince v = 00 = v₀² + 2ada = -v₀²/(2d)a = -(15.2778 m/s)/(2 * 38m) a = -3.2418 m/s²find net force and you find friction.f = ma f = (1165 .2418 m/s²)f = 3776.7 n = ffw = ff · dw = (3776.7 n)(38 m)w = -1.4 × 10^5 jthe friction forces do 1.4 × 10^5 j of work on the car