Question

1. An object with a mass m = 2.0 kg placed on a rough horizontal plane is connected to a spring with a spring constant k = 1000 N/m.
When shrinking the spring x = 2.0 cm after releasing your hand, answer the following questions. Note, the friction coefficient is μ = 0.50.
(1) Find the work Ws that the spring did before returning to it's natural length.
(2) Find the work Wf that the frictional force did during this time.
(3) Find the net job W.

Answer 1

Part 1) When the spring is suppressed x = 2.0 cm the force exerted by the spring on the mass is

Work done by the spring is

So work done by the spring Ws = 10 J

Part 2)

Frictional force

Work done is given as

Since the block is moving to the right and friction force is acting to the left so work is negative

Part 3)

Net work done is given as