Which contact force always acts against the direction of movement? a. spring b. normal c. friction d. impact

B. friction

Explanation:

B. friction

This question should be in physics.

C.) Friction

Explanation:

A contact force is any force that is exerted when two objects are touching. Contact forces cannot be exerted if objects are not touching each other.  

 Friction is a force that acts between objects that are in contact. Friction always acts against the direction of movement, and it slows, stops, or prevents movement.

answer; i believe its called ; checks   and balances;