Answer:
16km/h
Explanation:
Vt=20km/h ---train speed
Vd=4km/h
Donas speed relative to ground is:
Vrd=Vt-Vd
Donas is moving in opposite direction of train .
Vrd=20km/h-4km/h
Vrd=16km/h
Solar energy is a good alternative to replace fossil fuel as the major energy source because solar power is renewable at absolutely no cost to supply energy infinitely.
The correct choice is Buffers.
Buffers contains both acids and bases in equilibrium.when base is added to buffers, they adjust the pH value by releasing hydrogen ions.when acid is added to buffers, they adjust the pH value by consuming hydrogen ions. hence these substances resist any change in their pH value by releasing or absorbing hydrogen ions.This process keeps the pH value constant.
Answer:
Particles vibrate parallel to the direction the sound travels
Using the combined gas law of P1V1=P2V2 and plug it in you get (4)V1 for you don't have initial volume = (0.2)(500) --> 4V1=100, divide by the coefficient on both sides and you get V1=25