Solving Spring and Block: Find Block Speed

[grouchy]

[SOLVED] Spring and Block

A spring is compressed 6 cm and an 6 kg block is placed against it. when the spring is released the block shoots forward along a rough, horizontal surface traveling 1.2 m before coming to a stop. The coefficient of kinetic friction between the block and the surface is 0.4. Find the speed acquired by the block as it leaves the spring.




I try to use conservation of energy but I'm having trouble since I'm not given k or v (find k would be the second question).

 

[Doc Al]

Although the problem does not make it clear, let's assume that the 1.2 m does not include the 6 cm that the spring expands. Further, assume that the rough surface only begins after the spring has expanded.

The block leaves the spring with some speed. What happens to its KE? How much work is done by friction?

 

[grouchy]

GOT it, I kept assuming that I need to use the potential of the spring. All i need was..

1/2mv^2 = k(coefficient of kinetic friction)Nd
v = square root of (2kNd/m) = 3.07 m/s matches up perfect

Also, I used the 1.2 m for d.

thx.