6. A girl pushes her little brother on his sled with a force of 300 N for 750 m. a. How much work is this?
b. How much energy is used?
c. How much power does she use if it takes her 25s?
d. How much power does she use if she runs and complete the 750m in 10s?

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?