a uniform metre rule balances on a knife edge at the 60cm mark a weight of 20N is suspended at one end calculate the weight of the metre rule
To calculate the weight of the meter rule, we need to consider the equilibrium condition of the meter rule.
The weight of the meter rule can be determined by applying the principle of moments. The principle of moments states that for an object to be in equilibrium, the sum of the clockwise moments about any point must be equal to the sum of the anticlockwise moments about the same point.
In this case, we can choose the knife edge as the pivot point. So, the anticlockwise moments would be the weight of the meter rule acting at its center of gravity (which is at the 50 cm mark), and the clockwise moment would be the weight of the suspended 20N weight.
Let's label the weight of the meter rule as 'W' and the distance of the weight of the meter rule from the pivot point as 'd'. The distance of the suspended weight from the pivot point is 60 cm.
Now, using the principle of moments, we have:
20N × 60cm = W × d
Simplifying the equation, we get:
1200 Ncm = W × d
Since the meter rule is uniform, we know that the center of gravity is at the halfway point (50 cm), so the distance 'd' is 10 cm.
Substituting the values, we have:
1200 Ncm = W × 10 cm
Simplifying further:
120 N = W × 10
Finally, isolating W, we divide both sides of the equation by 10:
W = 120 N / 10
Therefore, the weight of the meter rule is 12 N.