Experiencing Jerk

A vehicle was at rest for a long time. Suddenly it started moving. If the rate of increase in its acceleration in short interval of time is d a d t = 2 m s e c 3 \frac{da}{dt}=2 \frac{m}{sec^{3}}

Then find its displacement from its starting point after 6 seconds of its motion.


The answer is 72.

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.

5 solutions

Credits goes to Razvan Barbu. I just did the LaTeX job

We already know the law of linear movement at constant acceleration rate to be ( displacement ) x = x 0 + v 0 t + 1 2 a t 2 x = x_0+ v_0t +\frac{1}{2}at^2 If the acceleration is not constant, but increases at a constant pace, we simply introduce a new concept of Accelerated acceleration , the Jerk, j . The formula becomes: X = x o + v o t + 1 2 a t 2 + 1 2 × 1 3 j t 3 X = x_o + v_o t +\frac{1}{2}at^2 +\frac{1}{2}\times\frac{1}{3}jt^3 Where, Time, t = 6 s e c t = 6 sec Initial Position, x 0 = 0 x_0= 0 Initial Velocity, v 0 = 0 v_0=0 Initial Acceleration, a 0 = 0 a_0 = 0 Accelerated Acceleration, Jerk, j = 2 m s 3 j= 2ms^{3} Solution: X = 0 + 0 + 0 + 1 6 2 × 6 3 = 2 36 = 72 m X = 0 + 0 + 0 +\frac{1}{6}2\times 6^3= 2*36 =72m

Razvan Barbu
Mar 25, 2014

We already know the law of linear movement at constant acceleration rate to be ( displacement ) X = Xo + Vo t + ( A t^2 ) / 2 If the acceleration is not constant, but increases at a constant pace, we simply introduce a new concept of "accelerated acceleration" - Aa. The formula becomes: X = Xo + Vo t + ( Ao t^2 ) / 2 +( Aa t^3 ) / 6
where t - time = 6 seconds, Xo - initial position = 0, Vo - initial velocity = 0, Ao - initial acceleration = 0, Aa - "accelerated acceleration" = 2. Solution: X = 0 + 0 + 0 + ( 2
6^3 ) / 6 = 2*36 = 72m

Can't you please format it with LaTeX ?

It'd be nice!

Muhammad Arifur Rahman - 5 years, 10 months ago
Alex Mathew
Mar 24, 2014

Guys, there is a mistake in this question.its actually unsolvable without an initial condition for acceleration."initially at rest " simply implies v(t=0)=0 not a(t=0)=0.Therefor upon first integration we gets a=2t+C where C is a constant and finally S=(t^3)/3+C(t^2)/2.I solved it by assuming C=0.actually one more initial condition was needed.

I ran into the same problem and made the same assumption. The problem should really say initial acceleration equals zero.

A Former Brilliant Member - 7 years, 2 months ago

Thanks for pointing out. I've added some words to the question to cover your point.

Soham Zemse - 5 years, 10 months ago
Amit Kumar singh
Mar 21, 2014

da/dt =2. hence a = 2t (BY INTEGRATION). NOW a = dv/dt, INTEGRATING AGAI WE GET v = (t)(t). NOW V = ds/dt, INTEGRATING AGAIN WITH LIMITS WE GET S=72M

Venture Hi
Mar 13, 2014

first integration of 2 m/s^3 gives you acceleration, 2t. Second integration gives you speed, 2t^2/2 or t^2. Third integration gives you distance, t^3/3. In 6 seconds, the car would have moved a distance of 6^3/3= 72m

0 pending reports

×

Problem Loading...

Note Loading...

Set Loading...