Free body diagram with circular motion

[crybllrd]

Homework Statement

In a circular rotating room (think Gravitron), there are two blocks stacked against the wall and do not drop. Block A is touching block B, and block B is touching the wall.

Homework Equations

The Attempt at a Solution

I know how to do this problem, but I am not sure about where to draw the friction vectors. My intuition tells me straight up, but it seems like my instructor did something different.

 

[PhanthomJay]

Homework Statement

In a circular rotating room (think Gravitron), there are two blocks stacked against the wall and do not drop. Block A is touching block B, and block B is touching the wall.

Homework Equations

The Attempt at a Solution

I know how to do this problem, but I am not sure about where to draw the friction vectors. My intuition tells me straight up, but it seems like my instructor did something different.

the friction force opposes the direction of relative motion or pending relative motion between the 2 objects.

 

[ƒ(x)]

What about acceleration?

 

[PhanthomJay]

What about acceleration?

What's the direction of the acceleration? What force or forces provides the acceleration??

 

[crybllrd]

What about acceleration?

Constant speed.
OK I guess I was right, I must have gotten it confused with another lecture.
Thanks a lot!

 

[PhanthomJay]

Constant speed.
OK I guess I was right, I must have gotten it confused with another lecture.
Thanks a lot!

Well, you got the direction of the friction force correctly, but not the question about the acceleration. The acceleration of objects moving in a circle is inward toward the center of the circle (centripetal aceleration). Since there is a centripetal acceleration, there must be a centripetal force acting inward for it to accelerate inward (Newton2). That centripetal force is provided by the normal force between the books or book and wall. If there is no normal force, there can be no friction (Friction force less than or equal to u_s(N))!