Distance= speed * time
So multiply speed and time to get the value of distance
20*9.8 =196 meters
It changes because force is somewhat like pressure. Force is continuously against the object so as a result, speed changes .
<h2>
Answer:</h2>
400N/m
<h2>
Explanation:</h2>
When n identical springs of stiffness k, are attached in series, the reciprocal of their equivalent stiffness (1 / m) is given by the sum of the reciprocal of their individual stiffnesses. i.e
= ∑ⁿ₁ [
] -----------------------(i)
That is;
=
+
+
+ . . . +
-------------------(ii)
If they have the same value of stiffness say s, then equation (ii) becomes;
= n x
-----------------(iii)
Where;
n = number of springs
From the question,
There are 3 identical springs, each with stiffness of 1200N/m and they are attached in series. This implies that;
n = 3
s = 1200N/m
Now, to calculate the effective stiffness,m, (i.e the stiffness of a longer spring formed from the series combination of these springs), we substitute these values into equation (iii) above as follows;
= 3 x 
= 
= 
Cross multiply;
m = 400N/m
Therefore, the stiffness of the longer spring is 400N/m
I believe it’s nuclear energy.
Answer:
A. When two surfaces are moving relative to each other.
Explanation:
It is also know as dynamic friction