The friction arrow in an FBD for a moving object point is in opposite way to motion. Because friction always works in the opposite direction of the motion of the object.
Answer: Option D
Explanation:
When two object come into contact, the contact force come into play. Now, one component of the contact force i.e. the normal forces act perpendicularly at the direction of motion. Whereas, the frictional forces always acts parallel at the direction of the force acting on the object but in the opposite way.
For example, if we slide a book on the table to the right hand side, the exact equal and opposite frictional force will induce in the opposite direction, tempting to reduce the motion.
