Formula
F = k*x
Givens
F = 21 N
x = 13
K = ?
Solution
21 = 13 k
21/13 = k
k = 1.615 N / cm
The units are not quiet the ones you should be using. Newtons are found in the mks system.
13 cm [1 m / 100 cm ] = 0.13 m
So an alternate solution is
21 N = k * 0.13 m
k = 21 N / 0.13 m
k = 161.5 Newtons / meter. Answer
" An object<span> at rest stays at rest and </span>an object <span>in motion stays in motion with the same speed and in the same direction </span>unless acted upon<span> by an </span>unbalanced force<span>."- Newtons first Law of Motion
Also, velocity is the speed of something in a given direction (So, 50mph North is an example of velocity)</span>
Answer:

31.29 m/sec
Explanation:
We have given density of substance 
We have convert this into
We know that 1 lb = 0.4535 kg. so 0.14 lb = 0.14×0.4535 = 0.06349 kg
We know that 1 kg = 1000 g ( 1000 gram )
So 0.06349 kg = 63.49 gram
And we know that 1 gram = 1000 milligram
So 63.49 gram 
We know that 
So 
So
=\frac{63.49\times 10^3}{0.2249\times 10^{-5}}=276.74\times 10^8lb/m^3[/tex]
In second part we have to convert 70 mi/hr to m/sec
We know that 1 mi = 1609.34 meter
So 70 mi = 70×1609.34 = 112653.8 meter
1 hour = 3600 sec
So 70 mi/hr 