# Homework Help: Help quickly

1. Jan 10, 2005

### Port

Help quickly plz

I need help on this and quick!:
A 4kg block is pushed alomng the ceiling with a constant apllied force of 85N that acts at an angle of 55 degrees with the horizontal. The block accelerates to the right at 6m/s^2. detremine the coefficient of kinetic friction between the block and the ceiling.

ok i worked out the problem but i got the wrong answer. the values i got are: for normal force=69.62N. for ap=12.19. for af=6.19. for Ff=24.8N final answer=.356 and i need .816 what did i do wrong?

2. Jan 10, 2005

### dextercioby

Check the numbers in the text of the problem.That block should be flying...

Daniel.

3. Jan 10, 2005

### Port

what do u mean the numbers in the problem are right???

4. Jan 10, 2005

### dextercioby

1.U double posted.Two threads on the same problem.It's not fair... :grumpy:
2.Yes,by the looks of it,the normal force should be zero and the body should raise from the ground...

Daniel.

5. Jan 10, 2005

### Yapper

Dex, its being pushed agaisnt the ceiling...

6. Jan 10, 2005

### Port

wait but why if someone is pushing it on the ceiling? ur confusing me!

7. Jan 10, 2005

### Yapper

OOHHHH I know, we forgot to account gravity, get the normal force, subtract or add gravity, im to tired to think, and then divide by Ff!!! see which one works

8. Jan 10, 2005

### dextercioby

Sorry,didn't read that part. You're right...It doesn't fly away...

Daniel.

9. Jan 10, 2005

### Port

wait what? how do i add or subtract gravity?

10. Jan 10, 2005