Question

Let's begin by determining the equilibrium position of a seesaw pivot. You and a friend play on a seesaw.Your mass is____

Answer 1

Answer:

1.2 m from the left end

Explanation:

$M$ = mass of the person = 90 kg

$m$  = mass of friend = 60 kg

$r$  = distance of pivot from the person or from the left end

$L$  = length of the seesaw board = 3.0 m

$s$  = distance of pivot from the friend or from right end = L - r = 3 - r

Using equilibrium of torque about the pivot

$M g r = m g s\\(90) r = (60) (3 - r)\\90 r = 180 - 60 r\\90 r + 60 r = 180 \\150 r = 180 \\r = 1.2$