A man who weight 90kgf is balanced by a small boy 30kgf who sits metres from the fulcrum of a seesaw. At what distance on the fulcrum is the man sitting
supply the missing distance, and then solve just as you did the last one.
Note that since the man weighs 3 times as much, the boy must sit 3 times farther away from the fulcrum.
To solve this problem, we can use the concept of a lever and the principle of moments.
The principle of moments states that the sum of the anti-clockwise moments is equal to the sum of the clockwise moments about a fixed point (fulcrum) in equilibrium. In this case, the boy and the man are balanced, so the total moment on one side of the fulcrum must be equal to the total moment on the other side.
Let's assume the distance of the boy from the fulcrum is "x" meters, and the distance of the man from the fulcrum is "y" meters.
The moment of the boy can be calculated by multiplying his weight (30kgf) by his distance from the fulcrum (x meters).
The moment of the man can be calculated by multiplying his weight (90kgf) by his distance from the fulcrum (y meters).
Since the system is balanced, the sum of the moments of the boy and the man must be zero.
So, we can set up the equation:
(30kgf) * (x meters) = (90kgf) * (y meters)
Simplifying the equation, we get:
30x = 90y
To find the distance of the man from the fulcrum (y), we need to solve for y. We can rearrange the equation and substitute the values:
y = (30x) / 90
y = x / 3
Therefore, the man is sitting one-third the distance from the fulcrum compared to the boy.
In simpler terms, if the boy is sitting 3 meters away from the fulcrum, the man would be sitting 1 meter away from the fulcrum.