<u><em>Diffusion:
</em></u><em> in diffusion particles move from area of higher concentration to the area of lower concentration..
</em><u><em>causes:
</em></u><em>the movement of particles allow them ti disperse,,, when molecules are close to each other they collide with each other and push each other apart so they spread in the whole area... :)</em><u><em>
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Answer:
Their speed in a vacuum is a constant value.
Explanation:
Electromagnetic waves consits of oscillations of electric field and magnetic field. The oscillations of these fields occur in a direction perpendicular to the direction of propagation of the waves, so they are transverse wave. Electromagnetic waves, contrary to mechanical waves, do not need a medium to propagate, so they can also travel through a vacuum. In a vacuum, their speed is constant and has always the same value, the speed of light:

Answer:
matter is the correct answer.
solution:
We know v0 = 0, a = 9.8, t = 4.0. We need to solve for v
so,
we use the equation:
v = v0 + at
v = 0 + 9.8*4.0
v = 39.2 m/s
Now we just need to solve for d, so we use the equation:
d = v0t + 1/2*a*t^2
d = 0*4.0 + 1/2*9.8*4.0^2
d = 78.4 m
The added weight of the sand puts more downward pressure on the wheels contacting the rails, which would cause the trains speed to decrease.