Does Friction Oppose Motion on an Inclined Surface?

AI Thread Summary
Friction always acts in the opposite direction to the relative motion between an object and the surface it is on. When an object moves on an inclined surface, friction opposes its motion, not moving in the same direction. For example, if a brick is dropped onto a moving plank, friction will accelerate the brick in the direction of the plank's motion until they move at the same speed. This demonstrates that friction seeks to equalize the motion of the object with that of the surface. Thus, friction does not move in the same direction as the object but rather opposes its relative motion.
Nstraw
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If we Are moving an object on an inclined surface than shouldn't friction be in the same direction?
 
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Nstraw said:
If we Are moving an object on an inclined surface than shouldn't friction be in the same direction?
Same direction as what? The motion of the object?
 
Nstraw said:
If we Are moving an object on an inclined surface than shouldn't friction be in the same direction?

Friction is always in the opposite direction to the direction of movement of an object.
 
anjelin said:
Friction is always in the opposite direction to the direction of movement of an object.

Not exactly.
It opposes the RELATIVE motion the object has to say, the underlying surface.

That is:
Friction seeks to equalize the motions of the object and the surface.

Suppose you drop a brick (no horizontal velocity) onto a moving plank.
The friction from the plank will accelerate the brick in the direction of its own generated horizontal motion, until the brick moves with the same speed as the plank.
 
So friction will oppose the motion
 
Nstraw said:
So friction will oppose the motion

It opposes relative motion between the object and the surface.
 

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