Tarzan, played by Patrick Huard, 60 kg, must cross a stream 5 m wide, and full of hungry crocodiles. To do this, decides to slide along a sloping tree trunk, hollowed and moist so that there is no friction. After the trunk, there is a part of 3 m platform covered in mud, with a coefficient of kinetic friction of 0.3 leading to the edge of stream. It clings so, without jumping to a vine rigid 8 m with a massless, free to rotate (without friction), in lower end which is just below where it is attached (the vine hangs). The vine and he traveled an arc above the stream. Tarzan must release the vine when stops momentarily and land, dry, on the other side of stream! a) You must ensure that nothing bad will happen to Tarzan, and for this you must select the tree trunk to be used (starting height of Tarzan). b) The actor who plays the role of Tarzan wants to land on a chair mounted on a spring so as not to injure, is stipulated in his contract. This chair is 1 m above the ground and is attached to a spring can undergo a maximum compression of 0.3 m. What should be the spring constant of the spring to avoid damage to the actor?