# Two Blocks#

Two blocks, $$M =$$ 2$$m$$, sit on a horizontal frictionless surface with a compressed massless spring between them. After the spring is released $$M$$ has velocity $$v$$.

## Part 1#

What was the total energy initially stored in the spring?

• 3.0 $$mv^2$$

• 4.0 $$mv^2$$

• 8.0 $$mv^2$$

• 20.0 $$mv^2$$

• 6.0 $$mv^2$$