1. The acceleration equation of a certain particle is a=2t, after 4s, its velocity reaches 20m/s, then the initial velocity of the particle movement is ) ms B Sms 2.

Change in velocity is the integral of all the differential accelerations acting over the period of acceleration.

20 = u + t²

20 = u + 4² - 0²

20 = u + 16

u = 4 m/s

number of electrons for neutral cl

answer;

d. are made mostly of liquid

explanation;

-the general   composition and structure planets includes; they have a thick gas and liquid layer covering a small,solid core. mostly the gases are hydrogen and helium atmosphere and layers of liquid hydrogen. for instance neptune and uranus are examples of the outer planets, they have a core covered by ice and ammonia.

-neptune's atmosphere is hydrogen and helium with a bit of methane so there is no oxygen to breath and the interior is made up of frozen water and ammonia with a rock and iron core. thus, there is no liquid water or solid surface to survive.