# Calculate the forces of a mover pushing a crate

1. Apr 7, 2007

### raman911

1. The problem statement, all variables and given/known data
A mover pushes a 85kg crate along the floor at a constant speed through a displacement of 3,1m[E]. The coefficient of kinetic friction between the floor and crate is 0.22.
A) Calculate Fn and Fapp.

3. The attempt at a solution
Fg=mg
=85kg*9.8N/kg
Fg=833N
So Fn=Fg
but how can i find Fapp

2. Apr 7, 2007

### denverdoc

You may want to review friction;

Fn=weight since it is vertical. But frictional force is a fraction of this. Hint:There is a constant that you are not using.

3. Apr 7, 2007

### chouZ

make a body diagram and it will be more clear. Net force of the forces in the direction of the displacement equal the product of mass and acceleration. Solve for Fapp..

4. Apr 7, 2007

### chouZ

Net force= forces applied on the axis of the displacement

5. Apr 7, 2007

### raman911

i don't know net force

6. Apr 7, 2007

### arildno

Sure you do.
You know the crate moves with constant velocity.

What does that mean, in terms of net force acting upon the crate?

7. Apr 7, 2007

### raman911

i don't understand that

8. Apr 7, 2007

### arildno

If an object moves with constant velocity, what is its acceleration?
And how is acceleration tied together with forces?

9. Apr 7, 2007

### raman911

but i need time to find acceleration

10. Apr 7, 2007

### arildno

Eeeh, why?

11. Apr 7, 2007

### harmonicmotion

i need help with AP Physics free response questions

12. Apr 7, 2007

### harmonicmotion

its the 2002 ap physics c queston

13. Apr 7, 2007

### arildno

14. Apr 7, 2007

### harmonicmotion

could someone reply if they are willing to help

15. Apr 7, 2007

### raman911

$$Given$$

$$m=0.2kg$$
$$\Delta {h}_{2}=0m$$
$${v}_{2}=3.96m/s$$

$$Required$$

$${E}_{g} and {E}_{k}$$

$$Solution$$

$${E}_{g}={m}g\Delta h$$
$$={0.2kg}*9.8N/kg*0m$$
$${E}_{g}=0J$$

$${E}_{k}=(1/2)m{v}_{2}^2$$
$$=(1/2)0.2Kg(3.96m/s)^2$$
$${E}_{k}=1.56J$$

Last edited: Apr 8, 2007