If a person weighs 140 lb on earth their weight in newtons is

623.6N

Explanation:

There are 2.2 pounds in one kilogram, so you must divide 140 lb by 2.2 to convert the units to kilograms.

140/2.2 = 63.6 kg

The gravitational force also known as weight would equal mass times acceleration due to gravity.

Fg = (63.6 kg)(9.8 m/s^2) = 623.6N

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answer: 2×10^-2kg

explanation: density= mass per volume

vol=mass/density

converting to s.i units we have;

3÷1000kg = 0.003

1.5÷100m = 0.15

0.003/0.15 = 0.02kg