What is the weight in newtons of an object that has a mass of (a) 8 kg, (b) 0.04 kg, and (c) 760 Mg?

_{Statics of Rigid Bodies 14^th Edition by RC Hibbeler, Problem 1-1}

Solution:

Part A: To convert the given mass in kilogram to newton force, we simply need to multiply by the acceleration due to gravity of 9.81 m/s². We need to take into account that 1\:\text{kg m/s}^2\:=1\:\text{N} .

\begin {aligned}

8\:\text{kg} & =8\:\text{kg}\times 9.81\:\text{m/s}^2 \\
&=78.48\:\text{N}

\end {aligned}

Part B: Using the same principle from Part A, we have

\begin {aligned}

0.04\:\text{kg}&=0.04\:\text{kg}\times 9.81\:\text{m/s}^2\\
&=0.3924\:\text{N}

\end {aligned}

Part C: So, we are given 760 Mg (megagram). We know that 1 Mg is equivalent to 1000 kg. Therefore, 760 Mg is equal to 760,000 kg. Therefore, we have

\begin {aligned}
760\:000\:\text{kg}&=760\:000\:\text{kg}\times 9.81\:\text{m/s}^2\\
&=7\:455\:600\:\text{N}
\end{aligned}