Answer:

Explanation:
The magnitude of the electrical force between the two point charges is

where
k is the Coulomb's constant
is the magnitude of each charge
r = 3.00 m is the separation between the two charges
Substituting the numbers into the formula, we find

Answer: 1.95
Explanation:
You should start off from the decay formula and solve for τ:


Apply inverse logarithmic function:

The final form will be:

Inputing values for I, IO, and t:
A uniform thin solid door has height 2.20 m, width .870 m, and mass 23.0 kg. Find its moment of inertia for rotation on its hinges. Is any piece of data unnecessary? So far, I don't understand how to calculate moments of inertia for things like this at all. I can do a system of particles, but when it comes to any ridgid objects, such as this door or rods or cylinders, I don't get it. So basically I have no idea where to even start with this.
so A
Kinetic energy is the energy for a catapult.