A boy of mass 40kg sits at point of 2.0m from the pivot of see saw . Find the weight of a girl who can balance the see saw by sitting at a distance of 3.2 m from the pivot . (Take g = 10 Nkg-1)
I need an answer
40 kg * 2.0 m = x kg * 3.2 m
find the mass , multiply by g to get weight (in Newtons)
To now the calculate
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To find the weight of the girl who can balance the see-saw, we need to consider the principle of moments.
The principle of moments states that for an object to be in rotational equilibrium, the sum of the moments acting on it must be zero.
In this case, the moment of the boy sitting at 2.0m is equal to the moment of the girl sitting at 3.2m.
The moment of a force can be calculated by multiplying the force by the perpendicular distance from the pivot.
Let's proceed with the calculations step by step:
1. Calculate the moment of the boy:
Moment_boy = Mass_boy × Distance_boy × g
= 40 kg × 2.0 m × 10 N/kg
= 800 Nm
2. Since the see-saw is balanced, the moment of the girl will be equal to the moment of the boy:
Moment_girl = Moment_boy
Mass_girl × Distance_girl × g = Moment_boy
3. Rearrange the equation to find the weight of the girl:
Mass_girl = Moment_boy / (Distance_girl × g)
= 800 Nm / (3.2 m × 10 N/kg)
= 800 N / 32
= 25 kg
Therefore, the weight of the girl who can balance the see-saw by sitting at a distance of 3.2m from the pivot is 25 kg.