Calculating Moment of Force for 300kg Crate Around Support A | 3000N Force

[John78]

Homework Statement

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

Homework Equations

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

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.

 

[bilal ahmed]

It's easy

 

[John78]

not for every one :C

 

[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

 

[John78]

I know only that crate = 300 kg

 

[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?

 

[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.