Location, Velocity, Acceleration, Jerk, Snap, Crackle and Pop.

This problem's question: How fast in m/s is the test particle moving when it reaches 997.5 m?

All distance units are meters. All time units are seconds.

I am defining a few terms for this problem: jerk = acceleration t , snap = jerk t , crackle = snap t \text{jerk}=\frac{\partial \text{acceleration}}{\partial t},\, \text{snap}=\frac{\partial \text{jerk}}{\partial t},\,\text{crackle}=\frac{\partial \text{snap}}{\partial t} and pop = crackle t \text{pop}=\frac{\partial \text{crackle}}{\partial t} . Actually, jerk \text{jerk} is often defined as the derivative of acceleration \text{acceleration} with respect to time \text{time} , represented by t t here. Also, I am using l l as the initial location. Every parameter except pop \text{pop} for this problem has been set to 0 0 . Remember that velocity is the derivative of position with respect to time. Time in this problem is a positive real and time starts at 0 0 seconds.

The value of pop \text{pop} is 1 1000 m s 6 \frac{1}{1000}\,\frac{m}{s^6} for this problem.

The answer has been rounded the nearest integer m s \frac{m}{s} .


The answer is 200.0.

This section requires Javascript.
You are seeing this because something didn't load right. We suggest you, (a) try refreshing the page, (b) enabling javascript if it is disabled on your browser and, finally, (c) loading the non-javascript version of this page . We're sorry about the hassle.

2 solutions

Steven Chase
Jun 10, 2019

Here is another (very elementary) code solution. My notation denotes all quantities from the "zeroth derivative" to the "sixth derivative". The first derivative is the velocity, and the sixth derivative is the same as "pop".

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
import math

xd0 = 0.0
xd1 = 0.0
xd2 = 0.0
xd3 = 0.0
xd4 = 0.0
xd5 = 0.0
xd6 = 0.001

t = 0.0
dt = 10.0**(-6.0)

while xd0 <= 997.5:

    xd0 = xd0 + xd1 * dt  # Explicit Euler
    xd1 = xd1 + xd2 * dt
    xd2 = xd2 + xd3 * dt
    xd3 = xd3 + xd4 * dt
    xd4 = xd4 + xd5 * dt
    xd5 = xd5 + xd6 * dt

    t = t + dt

print dt
print t
print xd1

#1e-06
#29.9254670091
#199.996912521

Ah, a numerical solution to the differential equation.

DSolve [ { x ( 6 ) ( t ) = p , x ( 5 ) ( 0 ) = c , x ( 4 ) ( 0 ) = s , x ( 3 ) ( 0 ) = j , x ( 0 ) = a , x ( 0 ) = v , x ( 0 ) = l } , x , t ] position : t l + v t + a 2 t 2 + j 6 t 3 + s 24 t 4 + c 120 t 5 + p 720 t 6 \text{DSolve}\left[\left\{x^{(6)}(t)=p,x^{(5)}(0)=c,x^{(4)}(0)=s,x^{(3)}(0)=j,x''(0)=a,x'(0)=v,x(0)=l\right\},x,t\right] \Rightarrow \\ \text{position}: t\to l+v\,t+ \frac{a}{2} t^2+ \frac{j}{6} t^3+\frac{s}{24} t^4+\frac{c}{120} t^5+\frac{p}{720} t^6

With only pop \text{pop} non-zero and equal to 1 1000 m s 6 \frac{1}{1000} \frac{m}{s^6} , the formula simplifies to position : t 1 720 × 1000 t 6 \text{position}: t\to \frac{1}{720\times1000}t^6 .

Solving 1 720 × 1000 t 6 = 997.5 \frac{1}{720\times1000}t^6=997.5 gives t = 29.9254644949264 t=29.9254644949264 seconds.

Doing the first derivative of position with respect to time and substituting these parameters, including the solved for time gives an answer after rounding to the nearest integer of 200 m s 200\frac{m}{s} . This is about 447.4 mph.

0 pending reports

×

Problem Loading...

Note Loading...

Set Loading...