Unlock the Secret of a Gravity-Defying Parkour Stunt—With Physics!

We tin interruption that diagonal question down into horizontal and vertical portions; for present let's conscionable absorption connected the former. Say you commencement with a horizontal velocity (v₁) of –1 metre per 2nd and rebound with a horizontal velocity (v₂) of +1 m/s. The alteration of motion indicates the reversal of direction. Think of it similar you're moving backmost and distant on the x axis of a coordinate plane, antagonistic to the left, affirmative to the right.

Notice that your speed stays the same, but the velocity changes. (Remember, velocity has a direction.) In fact, because your horizontal velocity reverses, you get a large summation successful velocity. (v2 – v1) = (1 – (–1)) = 2. This gives you a larger interaction acceleration, a greater mean force, and much friction. The bouncing backmost and distant is the full cardinal to beating gravity successful this stunt.

So however overmuch unit would you request to exert to marque 1 of these rebounding partition jumps? Let's accidental you person a wide of 75 kilograms and a friction coefficient of 0.6, which is astir apt blimpish for rubber soles.

For starters, the frictional unit (F_f) indispensable adjacent oregon transcend the gravitational unit (mg). The gravitational tract spot connected Earth (g) is 9.8 newtons per kilogram. So the gravitational force, (m x g) = 75 x 9.8 = 735 newtons.

Now remember, the frictional unit is the mean unit times the coefficient of friction (F_f = μN). So to execute a minimum frictional unit of 735 newtons, we request a mean unit of astatine slightest 1,225 newtons (F_f/μ = 735/0.6 = 1,225).

Both of these forces, gravity and the mean force, are pushing connected you, truthful we request to adhd them up to get the nett force. Since they're perpendicular, we tin easy cipher the vector sum arsenic 1,429 newtons. (Take note, kids: You privation to beryllium a parkour hero? Take linear algebra.)

That means you request to propulsion backmost with the aforesaid unit (because forces are an enactment betwixt 2 things). 1,429 newtons is simply a unit of 321 pounds. That's important but not impossible. Doing it eight times successful accelerated succession, though? Not truthful easy.

How overmuch clip bash you person to bash the turnaround? With the mean unit and wide of the person, we tin cipher the horizontal acceleration a_x. By definition, that successful crook equals the alteration successful velocity per portion of clip (Δt), truthful we tin usage that to lick for the clip interval:

Plugging successful our numbers, we get a clip interval of 0.12 second. In different words, if you hesitate you fall. Bottom line, if you privation to bash this awesome parkour stunt you gotta beryllium strong, fast, and fearless—because if you tally abbreviated of newtons halfway up, the descent is simply a batch faster than the ascent.