Hello!
To answer your question, salt is a compound!
It is the product of the chemical bond between Na (Sodium) and Cl (Chloride),
Hopes this help you with your question.
Answer:

Explanation:
Assume that the distance travelled initially is d.
In order to stop the block you need some external force which is friction.
If we use the law of energy conservation:

a)
Looking at the formula you can see that the mass doesn't affect the distance travelled, as lng as the initial velocity is constant (Which indicates that the force must be higher to push the block to the same speed) therefore the distance is the same.
b) If the velocity is doubled, then the distance travelled is multiplied by 4, because the distance deppends on the square of the velocity.
<span>According to newton's second law of motion,the acceleration of an object equals the net force acting on the object divided by the objects "Mass"
Hope this helps!</span>