PRACTICE IT Use the worked example above to help you solve this problem. A proton is released from rest at x = ?2.00 cm in a constant electric field with magnitude 1.50 103 N/C pointing in the positive x-direction. (a) Assuming an initial speed of zero, find the speed of a proton at x = 0.0400 m with a potential energy of ?1.44 10-17 J. (Assume the potential energy at the point of release is zero.) m/s (b) An electron is now fired in the same direction from the same position. Find the initial speed of the electron (at x = ?2.00 cm) given that its speed has fallen by half when it reaches x = 0.110 m, a change in potential energy of 3.12 10-17 J. m/s NEED HELP WITH THIS PART ONLY PLEASE EXERCISE HINTS:GETTING STARTED | I'M STUCK! The electron in part (b) travels from x = 0.110 m (where it has half the initial speed you previously calculated) to x = ?0.240 m within the constant electric field. If there's a change in electric potential energy of ?8.41 10-17 J as it goes from x = 0.110 m to x = ?0.240 m, find the electron's speed at x = ?0.240 m. (Note: Use the values from the Practice It section. Account for the fact that the electron may turn around during its travel.) ANSWER IN M/S PLEASE