Answer:
Yes, the rocks are made of matter
Explanation:
Let's remember the definition of matter.
Matter is all that has mass and occupies a place in space. Therefore, if we measure the mass of each rock we will know its mass, the other fact is that rocks like any particular body are occupying a place in an empty space.
The opposite of this is antimatter and can its extent be given by the quantum mechanics.
Answer:
Sound waves are reflected back
Answer:
Electric field, 
Explanation:
It is given that,
Mass of sphere, m = 2.1 g = 0.0021 kg
Charge, 
We need to find the magnitude of electric field that balances the weight of a plastic spheres. So,
a = g
or
Hence, the magnitude of electric field that balances its weight is 
. Hence, this is the required solution.
The electromagnetic spectrum is the system of frequencies that show electromagnetic radiation, respective wavelengths, and photon energies. Some examples of frequencies found on the electromagnetic spectrum are radio waves, microwaves, infrared, optical, ultraviolet, X-rays, and gamma-rays.
