A Monkey Climbing A Rope – What Happens?


A monkey hangs on one end of a rope which passes over a pulley and is balanced by a weight on the other end; the weight is the same as the weight of the monkey. The monkey decides to climb the rope. What happens next?


As the monkey initiates its climb up the rope, a consequential shift in the equilibrium unfolds. The weight, initially counterbalanced by the stationary monkey, undergoes an ascent. The rationale behind this dynamic lies in the additional energy exerted by the climbing monkey, disrupting the delicate equilibrium and setting the weight in motion.

Delicate Balance Disturbed:

  1. Counterbalance Dynamics:
    • Stationary Equilibrium: Initially, when the monkey is stationary, a delicate equilibrium exists between the weight and the monkey. The gravitational forces of both entities balance each other out.

Monkey’s Ascent Alters the Equation:

  1. Introduction of Additional Energy:
    • Climbing Exertion: As soon as the monkey commences its climb, it injects extra energy into the system. The act of lifting its own weight disrupts the equilibrium by introducing an additional pull on the rope.
  2. Destruction of Counterbalance:
    • Shift in Forces: The climbing monkey’s exertion disrupts the counterbalance that previously existed. The introduction of a new force, driven by the monkey’s ascent, tips the scales and leads to a net upward force on the weight.

Resultant Effect: Weight Ascends

  1. Weight’s Ascension:
    • Consequence of Climbing Energy: The disrupted equilibrium triggers an upward motion in the weight. The climbing monkey’s additional pull on the rope imparts sufficient force to overcome the gravitational counterbalance, causing the weight to ascend.


The seemingly simple scenario of a monkey climbing a rope, counterbalanced by a weight, unveils the intricacies of equilibrium and the role of additional energy in altering the balance. As the monkey exerts itself to ascend, the equilibrium is disrupted, setting in motion a dynamic interplay of forces that results in the weight ascending as well. This scenario serves as a captivating illustration of the delicate equilibrium in physics, where even a climbing monkey can tip the scales and set the system in motion.

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