• 49-N block is pulled by a horizontal force of 50.0 N along a rough horizontal surface at a constant acceleration of 6 m/s². What is the coefficient of friction? Explain your answer.

Suppose that 27 j of work is needed to stretch a spring from its natural length of 6 m to a length of 9 m. (a) how much work is needed to stretch the spring from 12 m to 14 m? j (b) how far beyond its natural length will a force of 78 n keep the spring stretched?