Answer
(a) $weight = 2.06\times 10^{-9}~N$
(b) $weight = 1.21\times 10^{-6}~N$
(c) $weight = 10~pounds$
$m = 4.6~kg$
Work Step by Step
(a) $m = 210\times 10^{-6}~grams = 2.10\times 10^{-9}~kg$
$weight = mg = (2.10\times 10^{-9}~kg)(9.80~m/s^2)$
$weight = 2.06\times 10^{-9}~N$
(b) $m = 12.3\times 10^{-3}~grams = 1.23\times 10^{-6}~kg$
$weight = mg = (1.23\times 10^{-6}~kg)(9.80~m/s^2)$
$weight = 1.21\times 10^{-6}~N$
(c) $weight = (45~N)(\frac{1~pound}{4.448~N})$
$weight = 10~pounds$
$mg = 45~N$
$m = \frac{45~N}{9.80~m/s^2} = 4.6~kg$
