Principle of Moments: Balancing a Meter Rule

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Homework Statement

A metre rule is balanced at the 50 cm mark. If a mass of 5kg is placed 40 cm from the pivot at one end, what mass must be placed 30 cm from the pivot on the other end to balance the rule?

Homework Equations

M1 * G * D1 = M2 * G * D2

The Attempt at a Solution

M1 = 5kg
M2 = ?
D1 = 40 cm
D2 = 30 cm
G = 9.8

Therefore 5 * 9.8 * 40 = M2 * 9.8 * 30
= (5 * 9.8 * 40)/9.8 * 30
M2 = 6.66kg Is this correct?

 

[tvavanasd]

Yes.

 

[PhanthomJay]

Homework Statement

A metre rule is balanced at the 50 cm mark. If a mass of 5kg is placed 40 cm from the pivot at one end, what mass must be placed 30 cm from the pivot on the other end to balance the rule?

Homework Equations

M1 * G * D1 = M2 * G * D2

The Attempt at a Solution

M1 = 5kg
M2 = ?
D1 = 40 cm
D2 = 30 cm
G = 9.8

Therefore 5 * 9.8 * 40 = M2 * 9.8 * 30
= (5 * 9.8 * 40)/9.8 * 30
M2 = 6.66kg Is this correct?

Yes.