Which contact force always acts against the direction of movement

Around faucet handle is part of a(n) a. lever b. screw c. inclined plane d. wheel and axle

Three charge are arranged as shown in the diagram. the magnitude of the net electrical force acting on the +6 uc charge, rounded to the tenths place, is .

If two students are running down the hall toward each other, trying to get to class, and they have the same mass and acceleration, what will happen when they collide? will their forces cancel out or will each one experience a reaction?