4.24 .. The upward normal force exerted by the oor is 620 N on an elevator passenger who weighs 650 N. What are the reaction forces to these two forces? Is the passenger accelerating? If so, what are the magnitude and direction of the acceieration? 4.25 " A student with mass 45 kg jumps off a high diving board. Using 6.0 X 024 kg for the mass of the earth, what is the acceler- ation of the earth toward her as she accelerates toward the earth with an acceleration of 9.8 m/sz? Assume that the net force on the earth is the force of gravity she exerts on it. 4.15 ' An electron (mass = 9.]l X 1031 kg) leaves one end of a TV picture tube with zero initial speed and travels in a straight line to the accelerating grid, which is 1.80 cm away. It reaches the grid with a speed of 3.00 X 106 m/s. If the accelerating force is constant, compute (a) the acceleration; (b) the time to reach the grid; (c) the net force, in newtons. (You can ignore the gravita- tional force on the electron.)