BIO? (a) An ordinary flea has a mass of 210 µg. How many newtons does it weigh? (b) The mass of a typical froghopper is 12.3 mg. How many newtons does it weigh? (c) A house cat typically weighs 45 N. How many pounds does it weigh, and what is its mass in kilograms?

Solution to 18E Step 1 According to Newton’s second law of motion, F=ma For a body under effect of gravity, F=mg, where m=mass of the body, and g=acceleration due to gravity. Step 2 (a) Mass of an ordinary flea=210g =210x10 kg -9 F=210x10 kg X9.8 -6 F=2.058X10 N Thus weight of ordinary flea=2.058X10 N -6 (b) Mass of froghopper=12.3mg=12.3x10 kg -9 -9 F=12.3x10 kg X 9.8 F=120.59x10 N -9 Thus weight of the froghopper =120.59x10 N -9