Bobby does work to climb to the top of a 7 m hill. If Bobby and his sled have a combined mass of 45 kg, how much Potential Energy will Bobby have at the top of the hill? (Ignore friction in this problem.)

Two charged particles, q1 and q2, are located on the x-axis, with q1 at the origin and q2 initially at x1 = 12.2 mm. in this configuration, q1 exerts a repulsive force of 2.62 µn on q2. particle q2 is then moved to x2 = 18.0 mm. what is the force (magnitude and direction) that q2 exerts on q1 at this new location? (give the magnitude in µn.)