兩條Physics 問題 (答岩比5星)!?
1) A 63 kg hiker is dangling over the edge of an icy cliff. His partner (80 kg) is standing on icy ground holding a rope to keep the dangling hiker from falling. What coefficient of friction is needed to keep them from sliding?
2) Find the change in length of a spring with constant 750 N/m if it is used to pull a 75 kg gold bar across a surface (at a constant velocity) with a coefficient of friction of 0.45.
please answer with steps!! thx very much