# Moment of the force

1. Apr 14, 2012

### John78

1. The problem statement, all variables and given/known data

Calculate the moment of the force exerted by the crate around support A.

2. Relevant equations

crate = 300 kg
1 kg=10N
300Kg*10=3000N

3. The attempt at a solution

Ra*42 m = 3000N *6m
Ra = 428,57 N

Rb*42 m = 3000N *36m
Rb=2571,42 N

I just want to check whether my working is correct or not.
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

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2. Apr 14, 2012

### bilal ahmed

It's easy

3. Apr 14, 2012

### John78

not for every one :C

4. Apr 14, 2012

### Emilyjoint

It is not easy because you have not been told the size of the box!!!
The moment of the box = weight x distance of centre of mass from A

5. Apr 15, 2012

### John78

I know only that crate = 300 kg

6. Apr 15, 2012

### John78

My calculation looks like that

crate = 300 kg
1 kg=10N
300Kg*10=3000N

Ra*42 m = 3000N *6m
Ra = 428,57 N

Rb*42 m = 3000N *36m
Rb=2571,42 N

MA=3000N*6m-2571,42
MA=-89999,64

Ra+Rb=428,57+2571,42=2999,99=3000N!!!

So the answer is Ra = 428,57 N

Am I right i thinking?

7. Apr 15, 2012

### PhanthomJay

if you assume that the cm of the crate is at 6 m from the left, your calculations are good, ecept that you should round them off to about 400N and 2600 N, respectively.