Question

Anna and Grace sit next to one another and weigh a combined 8 pounds. They sit 2.25 m from the axis of rotation of a seesaw.  At what distance from the axis of rotation must a 2.40 kg combined weight Sarah and Hannah be positioned on the other side of the axis to balance the seesaw?  

Answer 1

Answer:

Given,

The combined weight of both Anna and Grace is M1 = 8 pounds, one pound = 0.4535 kg, so M1 = 8 x 0.4535 kg = 3.62 kg.

The distance between the axis of rotation and the first pair is x1 = 2.25 m.

The combined weight of the second pair Srah and Hannah is M2 = 2.40 kg.

We need to calculate the position of this pair from the axis of rotation on the other side to balance the seesaw. For this we need to equat the moments, therefore

M1.x1 = M2.x2

or x2 = M1.x1 /M2 = (3.62 kg) (2.25 m) / (2.40 kg) = 3.39 m.