What will the FBD of 2 blocks being pulled look like?

[lyn83716]

Homework Statement

Block A is on top of Block B, both are of equal mass and size. Block B is being pulled by a hook at a constant velocity. There is friction between the table and block B.

Homework Equations

[/B]
What will each FBD look like? Is there friction between Block A and Block B?

The Attempt at a Solution

What are the downwards forces acting on the bottom block (B)? Is it gravity as well as the normal force of the top block? Do those two added = the normal force of Block B?

Block A FBD:
-force of gravity of block a (Fga) pointing downwards which equals to the force of normal of block a pointing upwards(Fgn)
-friction between block a and block b? i don't know

Block B FBD:
-force of gravity pointing downwards, force of A on B pointing downwards
-normal force of b pointing upwards
-applied force pointing fwd
-force of kinetic friction pointing backwards

 

[haruspex]

What will each FBD look like?

You need to post your own attempt first, as per forum rules.

 

[gneill]

Hi lyn83716,

Welcome to Physics Forums.

Your post is all questions but with no attempt at solution(s) or thoughts on what you think will happen. Can you perhaps try to draw what you think the FBDs for the blocks will look like and show us so that helpers can critique the result (tell you where you're right and what might be incorrect)?

 

[lyn83716]

Homework Statement

Block A is on top of Block B, both are of equal mass and size. Block B is being pulled by a hook at a constant velocity. There is friction between the table and block B.

Homework Equations

[/B]
What will each FBD look like? Is there friction between Block A and Block B?

The Attempt at a Solution

What are the downwards forces acting on the bottom block (B)? Is it gravity as well as the normal force of the top block? Do those two added = the normal force of Block B?

Attempt:

Block A FBD:
-force of gravity of block a (Fga) pointing downwards which equals to the force of normal of block a pointing upwards(Fgn)
-friction between block a and block b? i don't know

Block B FBD:
-force of gravity pointing downwards, force of A on B pointing downwards
-normal force of b pointing upwards
-applied force pointing fwd
-force of kinetic friction pointing backwards

 

[lyn83716]

You need to post your own attempt first, as per forum rules.

I posted my own attempt in the replies

 

[lyn83716]

Hi lyn83716,

Welcome to Physics Forums.

Your post is all questions but with no attempt at solution(s) or thoughts on what you think will happen. Can you perhaps try to draw what you think the FBDs for the blocks will look like and show us so that helpers can critique the result (tell you where you're right and what might be incorrect)?

I posted the attempt in the reply

 

[gneill]

-friction between block a and block b? i don't know

Are blocks a and b moving with respect to each other, or is block a moving along with block b? Is the system accelerating?

 

[haruspex]

Attempt:

Block A FBD:
-force of gravity of block a (Fga) pointing downwards which equals to the force of normal of block a pointing upwards(Fgn)
-friction between block a and block b? i don't know

Block B FBD:
-force of gravity pointing downwards, force of A on B pointing downwards
-normal force of b pointing upwards
-applied force pointing fwd
-force of kinetic friction pointing backwards

Next step is to turn those into equations of the form ΣF=ma.