My tree house

Classical Mechanics Level 1

What is the minimum amount of work in Joules that a 60 kg man must do in order to climb up a tree house that is 3 meters high?

Details and assumptions

  • The acceleration of gravity is − 9.8 m/s 2 . -9.8\text{ m/s}^2.


The answer is 1764.

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David Mattingly by David Mattingly

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2 solutions

David Mattingly Staff
May 13, 2014

The force I need to exert to overcome the force of gravity on me is F = 60 × 9.8 = 588 F=60 \times 9.8=588 N. The minimum work is therefore 588 × 3 = 1764 J 588 \times 3=1764~J .

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Aamodini Jayaram
Oct 7, 2014

According to Work-Energy theorem, work done is nothing but change in energy (it can be either kinetic energy or potential energy). In this case, W=mgh. Substituting the given values, we get W= 60 X (-9.8) X 3 = (-) 1764 J. Negative sign indicates that the work is done against gravity.

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