The Newton’s law Nikolas would use to come up with this idea is the <span>Third law that states:
</span><span>When one body exerts a force on a second body, the second body simultaneously exerts a force equal in magnitude and opposite in direction on the first body.
</span>
So, in this case, let's name the first Body
A which is the skateboard and the second body
B which is <span>the compressed carbon dioxide in a fire extinguisher. Then, as shown in the figure below, according to the Third law:
</span>

<span>
</span>
(a) 328.6 kg m/s
The linear impulse experienced by the passenger in the car is equal to the change in momentum of the passenger:

where
m = 62.0 kg is the mass of the passenger
is the change in velocity of the car (and the passenger), which is

So, the linear impulse experienced by the passenger is

(b) 404.7 N
The linear impulse experienced by the passenger is also equal to the product between the average force and the time interval:

where in this case
is the linear impulse
is the time during which the force is applied
Solving the equation for F, we find the magnitude of the average force experienced by the passenger:

Gravity affet everything and it touches nothing.
Hope this helps!
New Moon
Waxing Crescent
First Quarter
<span>Waxing Gibbous
</span>Full Moon
<span>Waning Gibbous
</span>Last Quarter
Waning Crescent
;)