When a large rock is weathered into tiny pieces which add up the weight of the original rock, this demonstrates the law of conservation of matter.
According to this law the mass of an object doesn't change with time and also it does not depends on how the particles are arranged themselves.
Hence, option (C) is correct.
Answer:
B
Explanation:
Simply take all forces pointing to the right of the box as positive and all of the forces pointing to the left of the box as negative and add all values.
ΣF = 7 + 18 + (-20) = 5N to the right
D. velocity
Velocity depends on speed and direction
Answer:

Explanation:
Mass of a proton, 
Mass of an electron, 
The distance between the electron and the proton is, 
We need to find the mutual attractive gravitational force between the electron and proton. The gravitational force is given by :

Where G is the universal Gravitational constant

So, the force between the electron and proton is
.
Answer:
Explanation:
work done by applied force
= force x displacement
= 7.6 x 15 m
= 114 J .