Chemistry deals with the study of elements-- their properties, chemical reactions and their compounds. This science includes the study of how these elements or compounds are formed. The history of chemistry is divided to 4 periods.
Black Magic, Alchemy, Traditional Chemistry and Modern Chemistry comprised these periods.
How did the early chemists determine which of the substances are elements? Long time ago, chemists knew which substances could not be broken down and that mixtures are broken down through chemical means. Through the said process, they were able to identify which are elements from the substances they have tested.
Answers:
a)The balloon is 68 m away of the radar station
b) The direction of the balloon is towards the radar station
Explanation:
We can solve this problem with the Doppler shift equation:
(1)
Where:
is the actual frequency of the sound wave
is the "observed" frequency
is the velocity of sound
is the velocity of the observer, which is stationary
is the velocity of the source, which is the balloon
Isolating :
(2)
(3)
(4) This is the velocity of the balloon, note the negative sign indicates the direction of motion of the balloon: It is moving towards the radar station.
Now that we have the velocity of the balloon (hence its speed, the positive value) and the time (
) given as data, we can find the distance:
(5)
(6)
Finally:
(8) This is the distance of the balloon from the radar station
The second statement is false. The Sun is a star, but not the only star.
Answer: a) close together
Explanation: The electric field lines also represent the intensity of the field, in this sense for strong electric fields it is usually draw the lines close to each other. In constrast when they are far apart the electric field is weak.
