A spring with an unstrained length of 0.076 m and a spring constant of 2.6 N/m hangs vertically downward from the ceiling. A uniform electric field directed vertically upward fills the region containing the spring. A sphere with a mass of 5.09 10-3 kg and a net charge of +6.5 µC is attached to the lower end of the spring. The spring is released slowly, until it reaches equilibrium. The equilibrium length of the spring is 0.059 m. What is the magnitude of the external electric field?

Question

A spring with an unstrained length of 0.076 m and a spring constant of 2.6 N/m hangs vertically downward from the ceiling. A uniform electric field directed vertically upward fills the region containing the spring. A sphere with a mass of 5.09  10-3 kg and a net charge of +6.5 µC is attached to the lower end of the spring. The spring is released slowly, until it reaches equilibrium. The equilibrium length of the spring is 0.059 m. What is the magnitude of the external electric field?

Answer in N/C

Note: the way my teacher told me to solve it is to use the equation: mg+ kx=qE. I know i have to solve for E but I don't know what to plug in for (g). Any help would be great! Thanks

Brian · Answer

Youre summing forces so mg is force due to gravity g=9.8 There are three forces, kx the spring mg gravity and qE the field force