Which of the following motions has a straight line? A. Steady motion of the plane in the sky
B. Movement of people sitting in cars from Hanoi to ThaiNguyen
C. Movement of the clock hands
D. Movement of the cabin on the sun's rotation

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?