Thursday 13 June 2013

Bob e Joe, lavavetri

Two window washers, Bob and Joe, are on a 3.00-m-long, 345-N scaffold supported by two cables attached to its ends. Bob weighs 750 N and stands 1.00 m from the left end, as shown in Figure. Two meters from the left end is the 500-N washing equipment. Joe is 0.500 m from the right end and weighs 1 000 N. Given that the scaffold is in rotational and translational equilibrium, what are the forces on each cable? 


Risolviamo con equilibrio di forze e di momenti usando lo schema seguente per masse, distanze e tensioni funi.

T_o + T_d = m_a g + m_b g + m_c g

a m_a  + b m_b + c m_c  - d T_d = 0  (polo in o)

Dato che le masse e le distanze sono note, le due equazioni mi danno le due tensioni funi.