A 3-kg skateboard is rolling down the sidewalk at 4 m/s when it collides with a 1-kg skateboard that was initially at rest. If the 1-kg skateboard moves off at 6 m/s after the collision, what is the new velocity for the 3-kg skateboard?

2m/s

Explanation:

Using the law of conservation of momentum which States that the sum of momentum of bodies before collision is equal to the sum of their momentum after collision.

Momentum = mass × velocity.

Before collision:

Momentum of 3kg body moving at 4m/s = 3×4

= 12kgm/s

Momentum of 1kg skateboard initially at rest = 1×0

= 0kgm/s (the velocity 0m/s because the body is initially at rest)

After collision:

1-kg skateboard moves off at 6m/s. Its momentum after collision will be;

1×6 = 6kgm/s

For the 3kg body moving with an unknown velocity v, its final momentum will be;

3×v = 3v

Applying the law as stated above;

12+0 = 6+3v

12 =6+3v

12-6 = 3v

6 = 3v

v = 6/3

v = 2m/s

This means that the new velocity of the 3kg skateboard after collision is 2m/s

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.