## geerky42 3 years ago i have question

1. geerky42

heres the FBD of a block acceleration at friction horizontal surface: |dw:1349649866061:dw|

2. geerky42

my question is how does it affect the free body diagram if i place smaller block in front of it like this: |dw:1349649924401:dw| assume F is so big that the smaller block does not to fall? Do it has any force against F? Please explain it to me.

3. Fellowroot

How can the smaller block not fall?

4. imron07

|dw:1349650550178:dw|

5. geerky42

there is a friction between two blocks assume force applied to bigger block is so high that the friction prevents smaller block from falling. Is it possible? idk haha

6. geerky42

and the FBD of smaller block is this, right? |dw:1349650685060:dw|

7. geerky42

or should normal force face to the left? why?

8. imron07

Correct :)

9. imron07

No, the normal force is in correct direction.

10. geerky42

what i dont understand is shouldnt second normal force from block 1 and 2 cancel each other out?

11. geerky42

so it shouldnt exist?

12. imron07

N, it does not cancel each other. The forces act in different object.

13. geerky42

oic thank. you didnt answer this question: is it possible for force applied to bigger block to be so high that friction can prevents smaller block from falling?

14. imron07

I was going to answer that. Yes, it is possible. The magnitude of normal force on smaller block actually depend on magnitude of the force acted on large block. The larger the force, the larger normal force on smaller block. If the normal force on smaller block large enough, the friction is large too (f=uN). The friction prevents block from falling.

15. Fellowroot

is it possible for force applied to bigger block to be so high that friction can prevents smaller block from falling? Theoretically I'm sure its true. In real life hmmmm. Let me think. I guess if you think of the friction between them to be so great that them being together is like Velcro then sure.

16. geerky42

ok thanks, everyone, it was great helpful :)