Q. Three point charges are arranged on a line. Charge = +5 and is at the origin. Charge = -2.5 and is at = 5. Charge is at = 2.00 what is (magnitude and sign) if net force on is zero?

Q. A 500 g block slides along a frictionless surface at a speed of 0.35m/s .it runs into a horizontal mass less spring with spring constant 50N/m that extends outward from a wall. It compresses the spring and then is pushed back in the opposite direction by spring, eventually losing contact with the spring. The amount of time (in s) that blocks stays in contact with the spring is?