An object with a mass of 6 kg is hanging from a spring with a constant of 12 (kg)/s^2. If the spring is stretched by 1 m, what is the net force on the object?

1 Answer
Feb 7, 2016

46.8 N toward earth.

Explanation:

There are two forces acting on the object, the gravitational force on the object \vec{F_g} = m. \vec{g_{}} towards earth and the spring force \vec{F_k} = -k.\vec{x_{}}. The net force is the vector sum of these two.

Defining UP as positive and DOWN as negative,
\vec{x_{}} = -1.0m; \quad \vec{g_{}} = -9.8 ms^{-2}

\vec{F_{}}_{Net}=\vec{F_k}+\vec{F_g} = -k.\vec{x_{}}+m.\vec{g_{}},
\qquad\quad =-(12kgs^{-2})*(-1m)+(6kg).(-9.8ms^{-2}),
\qquad\quad =(12-15.8)kg.m.s^{-2} = - 46.8N,

A negative Net force means it points downward (toward earth).