Please Help! What is the equation for the mechanical advantage of a lever?

MA = length of effort arm / length of resistance arm

MA = length of effort arm + length of resistance arm

MA = length of effort arm * length of resistance arm

MA = length of resistance arm/length of effort arm

What is the most useful equation for electric power?

If gases like carbon dioxide and methane make up less than 1% of the total atmosphere, why is it important for scientists to monitor changes in percentages of these gases?

Large electric fields in cell membranes cause ions to move through the cell wall. the field strength in a typical membrane is 1.0 x 10 7 n/c. what is the magnitude of the force on a calcium ion with charge +e? what is its acceleration? is it possible for a particle with the same charge as as calcium to have a different acceleration if placed at this location? what would change the acceleration: mass of the particle? diameter of the particle?