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On a given planet, the weight of an object varies directly with the mass of the object. Suppose that an object whose mass is 4 kg weighs 12 N. Calculate the mass of another object that weighs 21 N. kg=

User Koloman
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SOLUTION

The weight(w) of an object varies directly with the mass(m) of the object.


w\alpha m

Introducing a constant k


w=km

Given


\begin{gathered} w=12N \\ m=4kg \end{gathered}

Substitute the values of the weight and mass in order to solve for k


\begin{gathered} 12=4k \\ k=(12)/(4)=3 \\ \therefore k=3 \end{gathered}

Hence, the equation connecting the weight and mass is


w=3m

Let us now solve for the mass given the weight to be 21N


\begin{gathered} 21=3m \\ m=(21)/(3)=7 \\ \therefore m=7kg \end{gathered}

Hence, the answer is 7kg.

User Sitansu
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