# An object with a mass of 4 kg is hanging from a spring with a constant of 2 (kg)/s^2. If the spring is stretched by  8 m, what is the net force on the object?

Feb 22, 2018

$\Sigma F = 23.2 N$ downwards

#### Explanation:

We know two forces are involved, one from the mass, and one from pulling the spring.

${F}_{1} = m g = 4 \cdot 9.81 = 39.24 N$ (the force pulling on the object)

${F}_{2} = k \Delta x = 2 \cdot 8 = 16 N$ (the force the the object exerts on the spring and vice versa)

We know that ${F}_{1}$ acts downwards, and ${F}_{2}$ acts upwards.

$\Sigma F = {F}_{1} - {F}_{2} = 39.24 - 16 = 23.24 \approx 23.2 N$ downwards