Answer:

Explanation:
From the attached file diagram, the total force acting on the charged box is the downward weight and the repulsive force acting in opposite to the weight force . Hence we can write the total force as

When fixed,F=o
Hence

The value of the acceleration is 16.2m/s^2
Answer:

Explanation:
<u>Density
</u>
The density of a substance is the mass per unit volume. The density varies with temperature and pressure.
The formula to calculate the density of a substance of mass (m) and volume (V) is:

We have a cube-shaped piece of copper of 4 cm of side length. The volume of the piece is:

Surprisingly, no other magnitude is required, thus the answer is:

According to the Law of conservation of momentum, the total momentum of the system before and after the collision remains same. The momentum may transfer from one object to another as a result of the impact, but the overall momentum of the system remains same.
So, the correct answer is option a.
The total initial momentum of all objects interacting with one another usually equals the total final momentum.