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Action and Reaction
Storyboard 
Newton's third principle defines that forces have to be generated in pairs so that their sum is zero. This implies that before an action there is always a reaction of equal magnitude but in the opposite direction.
ID:(755, 0)
Force on a wall
Description
If we attempt to exert force against a wall, we will notice that the main limitation is determined by the adherence of our shoes to the floor. If the floor is smooth, we will typically begin to slip, thereby limiting the force we are capable of exerting.
It is interesting to note that if we push in a non-horizontal manner, the vertical component will affect our vertical force against the floor. In other words, the vertical reaction to our action against the wall will result in an increase (if we are pushing more upward) or a decrease (if we are pushing more downward) in our weight.
ID:(11533, 0)
Walking
Image
Every time we walk, we need to propel our body with each step. To do this, we place our foot on the ground, and assuming it doesn\'t slide due to friction, our muscles exert a force on our body that propels it forward and transfers the reaction to the foot, which in turn transmits it to the ground (the planet):
Since the planet is enormous, we don\'t directly observe the effect of this reaction. However, if we are standing on a smaller object like a cylinder, we can induce its rolling motion by moving relative to our position on the cylinder while it rolls in the opposite direction.
ID:(11532, 0)
Model
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Calculations
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Target : Equation To be used 
Equations
$ \Delta p_A = m_i \Delta v_A $
Dp = m_i * Dv
$ \Delta p_R = m_i \Delta v_R $
Dp = m_i * Dv
$ F_A \equiv\displaystyle\frac{ \Delta p_A }{ \Delta t }$
F = Dp / Dt
$ F_R \equiv\displaystyle\frac{ \Delta p_R }{ \Delta t }$
F = Dp / Dt
$ F_R =- F_A $
F_R =- F_A
ID:(15475, 0)
Action and reaction
Equation
An important aspect of force is that it cannot be created out of nothing. Every time we attempt to generate a action force ($F_A$) (an action), a reaction force ($F_R$) will inevitably be generated with the same magnitude but opposite direction:
| $ F_R =- F_A $ |
In other words, forces always occur in pairs, and the sum of these pairs always equals zero.
ID:(10984, 0)
Medium force (1)
Equation
The force ($F$) is defined as the momentum variation ($\Delta p$) by the time elapsed ($\Delta t$), which is defined by the relationship:
| $ F_A \equiv\displaystyle\frac{ \Delta p_A }{ \Delta t }$ |
| $ F \equiv\displaystyle\frac{ \Delta p }{ \Delta t }$ |
ID:(3684, 1)
Medium force (2)
Equation
The force ($F$) is defined as the momentum variation ($\Delta p$) by the time elapsed ($\Delta t$), which is defined by the relationship:
| $ F_R \equiv\displaystyle\frac{ \Delta p_R }{ \Delta t }$ |
| $ F \equiv\displaystyle\frac{ \Delta p }{ \Delta t }$ |
ID:(3684, 2)
Variation of moment with constant mass (1)
Equation
In the case where the inertial Mass ($m_i$) is constant, the momentum variation ($\Delta p$) is proportional to the speed Diference ($\Delta v$):
| $ \Delta p_A = m_i \Delta v_A $ |
| $ \Delta p = m_i \Delta v $ |
As the momentum variation ($\Delta p$) is with the inertial Mass ($m_i$) and the speed Diference ($\Delta v$) equal to
| $ p = m_i v $ |
for the case where mass is constant, the change in momentum can be written with the moment ($p$) and the initial moment ($p_0$), which, combined with the speed ($v$) and the initial Speed ($v_0$), yields
$\Delta p = p - p_0 = m_i v - m_i v_0 = m_i ( v - v_0 ) = m_i \Delta v$
where the speed Diference ($\Delta v$) is computed with:
| $ \Delta v \equiv v - v_0 $ |
thus resulting in
| $ \Delta p = m_i \Delta v $ |
ID:(13998, 1)
Variation of moment with constant mass (2)
Equation
In the case where the inertial Mass ($m_i$) is constant, the momentum variation ($\Delta p$) is proportional to the speed Diference ($\Delta v$):
| $ \Delta p_R = m_i \Delta v_R $ |
| $ \Delta p = m_i \Delta v $ |
As the momentum variation ($\Delta p$) is with the inertial Mass ($m_i$) and the speed Diference ($\Delta v$) equal to
| $ p = m_i v $ |
for the case where mass is constant, the change in momentum can be written with the moment ($p$) and the initial moment ($p_0$), which, combined with the speed ($v$) and the initial Speed ($v_0$), yields
$\Delta p = p - p_0 = m_i v - m_i v_0 = m_i ( v - v_0 ) = m_i \Delta v$
where the speed Diference ($\Delta v$) is computed with:
| $ \Delta v \equiv v - v_0 $ |
thus resulting in
| $ \Delta p = m_i \Delta v $ |
ID:(13998, 2)