Answer:
The set of frequencies of the electromagnetic Waves emitted by the atoms of an element is called emission spectrum.
Answer:
(a) 
(b) 
(c) K.E. = 21.168 J
(d) 
Explanation:
Given:
- mass of a block, M = 3.6 kg
- initial velocity of the block,

- constant downward acceleration,

That a constant upward acceleration of
is applied in the presence of gravity.
∴
- height through which the block falls, d = 4.2 m
(a)
Force by the cord on the block,



∴Work by the cord on the block,


We take -ve sign because the direction of force and the displacement are opposite to each other.

(b)
Force on the block due to gravity:

∵the gravity is naturally a constant and we cannot change it


∴Work by the gravity on the block,



(c)
Kinetic energy of the block will be equal to the net work done i.e. sum of the two works.
mathematically:


K.E. = 21.168 J
(d)
From the equation of motion:

putting the respective values:

is the speed when the block has fallen 4.2 meters.
Answer:
It is because it cannot be used time again and again.
Answer:
vacuum have no air. so, the hot body will remain unchanged in temperature
Explanation:
If a student took seven science classes, his/her at score would be 1200.
<h3>What is a graph?</h3>
A graph is a relationship in which data is presented on the axes of cartesian coordinates. The presentation of the graph must be such that it is easy to read off the graph.
Now we can see that the graph is a plot of SAT scores versus the number of science classes that students take. In this case, the slope would tell us the score per subject of a student in the SAT.
a) The mathematical model that re[resents this graph is;
y =100x + 500
b) The slope of the graph must be obtained by the use of two points thus;
m = y2 - y1/x2 - x1
m = 600 - 500/1 - 0
m = 100
c) Using the relation;
y = mx + c
m = 100
c = 500
y = 100(7) + 500
y = 1200
Thus if a student took seven science classes, his/her at score would be 1200.
Learn more about graph:brainly.com/question/16608196
#SPJ1