Answer:
The reflection and rectilinear propagation of light helps in the formation of shadows and also tells light doesn't penetrate opaque materials.
In an uniform circular motion, the direction of the net force on the object is radially inward, passing through the center of the circle.
Answer:
protons (+ charge) & neutrons (neutral charge)
however protons has a positive charge so it determined what atom it is.
The De Broglie wavelength of the electron is

And we can use De Broglie's relationship to find its momentum:

Given

, with m being the electron mass and v its velocity, we can find the electron's velocity:

This velocity is quite small compared to the speed of light, so the electron is non-relativistic and we can find its kinetic energy by using the non-relativistic formula:
One day, as I was walking, I found some sandy soil beside the road.