Question

The picture below shows a boy climbing a rope ladder hanging from the branch of a tree. The boy in the picture finds it difficult to climb the ladder as it turns about the axis where he is holding. The instructor tells the boy to stretch the body with the hands stretched up and make the body parallel to the ladder and climb.

1. Which force caused the ladder to turn?
2. How does keeping the body parallel to the ladder make climbing easier?

Answer 1

1. The boy’s weight, acting downward through his centre of gravity, causes a turning effect (moment) on the ladder about the axis where he is holding it.
2. When the boy keeps his body parallel to the ladder, the perpendicular distance between the line of action of his weight and the axis of rotation becomes smaller. This reduces the turning effect on the ladder, making it easier to climb.