The 6 kg block is then released and accelerates
to the right, toward the 2 kg block. the
surface is rough and the coefficient of friction
between each block and the surface is 0.3 . the
two blocks collide, stick together, and move
to the right. remember that the spring is not
attached to the 6 kg block.
find the speed of the 6 kg block just before
it collides with the 2 kg block.
answer in units of m/s

5.709 m/s

Explanation:

Assuming compression of spring as 0.6m and spring constant of 602 N/m

The initial energy stored in the spring will be given by

By substitution, the initial energy is \

Kinetic energy of the 6 Kg block is given by subtracting energy lost due to friction from the initial stored energy hence

where m is mass, v is speed, g is acceleration due to gravity, x is the spring compression and is the coefficient of friction

Making v the subject then  

what experimental evidence led scientists to change from the previous model to this one?

a few of the positive particles aimed at a gold foil seemed to bounce back.

the colors of light emitted from heated atoms had very specific energies.

experiments with water vapor showed that elements combine in specific proportions.

cathode rays were bent in the same way whenever a magnet was brought near them.