I believe Intangibility is the answer! :P I hope this helps!
Answer:
a) 
b) 
c) 
Explanation:
the gravitational potential energy is given by:
The kinetic energy is given by:
the initial kinetic energy is zero because the motion started from rest, so:
applying the conservation of energy theorem:
The work done by the friction force is given by:
the angle of the force is 180 degrees because it's against the movement:
Answer choice C is a benefit of coal; all the others are negatives.
Feel free to ask me more questions; I'm happy to help. (Don't forget Brainliest!)
The <em>mass</em> of an object is a measure of how much stuff it's made of. So it's
a property of the object, like the object's length or color. It doesn't depend on
where the object is located right now, or on what else is around it..
The <em>weight</em> of an object is the measure of the gravitational force between it
and something else. The strength of the force depends on the size of both
masses, and also on how far apart they are. So the weight does depend on
where the object is located right now, and on what else is around it.
I think that sums it up fairly well.
