According to Hooke's law, Force = spring constant x displacement of the spring. Spring constant = Force/displacement in spring = 45/0.14 = 321.42 N/m. Hope this helps!
Answer:

T=157.06 N
Explanation:
Given that
Mass of first block = 21.1 kg
Mass of second block = 12.9 kg
First mass is heavier than first that is why mass second first will go downward and mass second will go upward.
Given that pulley and string is mass less that is why both mass will have same acceleration.So lets take their acceleration is 'a'.
So now from force equation

21.1 x 9.81 - 12.9 x 9.81 =(21.1+12.9) a

Lets tension in string is T


T=21.1(9.81-2.36) N
T=157.06 N
1) <span>yes;2
6*2=12
12*2=24
24*2=48
2)</span><span>Next Term (or nth term) = ar^n-1
</span>
a = first term, i.e. 5
<span>r = common ratio i.e. 3 (as 15/5=3 and 45/15=3 </span>
<span>n = .. </span>
<span>as you already have 1st , 2nd and 3rd terms</span>
<span>substituting now </span>
<span>T4= ar^n-1 </span>
<span>= 5*3^4-1 </span>
<span>= 5*3^3 </span>
<span>= 5*27 </span>
<span>T4 = 135
</span>T5= ar^n-1
<span>= 5*3^5-1 </span>
<span>= 5*3^4 </span>
<span>= 5*81 </span>
<span>T5 = 405 </span>
The true statements are B and C.
This comes from the following facts:
Even when heat is added to a substance in a change of phase the temperature does not increases since this heat is latent heat.