Experiencing Jerk

A vehicle was at rest. 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.

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4 solutions

Chetan Yadav
Mar 14, 2014

da/dt=2

da=2dt

integrating from 0 to t, we get

a=2t

dv/dt=2t (as a=dv/dt)

dv=2tdt

integrating

v=t*t

dx/dt=t*t (as v=dx/dt)

dx=t*t dt

integrating from o to t

x=(t * t * t)/3

when t=6

thus x= 72

Gaurav Khandelwal
Mar 14, 2014

a=2t then v=t^2 then s=t^3/3 then integrate 0 to 6 s=72

Md Lokman Hosen
Jun 2, 2016

G i v e n Given t h a t that d a d t \frac{da}{dt} = 2 2 or, d a da = 2 d t 2dt or, d a \int\ da = 2 d t \int\ 2dt or, a a = 2 t 2t or, d v d t \frac{dv}{dt} = 2 t 2t or, d v dv = 2 t d t 2tdt or, d v \int\ dv = 2 t d t \int\ 2tdt or, v v = t 2 t^2 or, d x d t \frac{dx}{dt} = t 2 t^2 or, d x dx = t 2 t^2 d t dt or, d x \int\ dx = t 2 d t \int\ t^2dt or, x x = t 3 3 \frac{t^3}{3} n o w now p l u g g i n g plugging t h e the l i m i t s limits 0 0 t o to 6 6 w e we g e t get x x = 6 3 3 \frac{6^3}{3} - 0 3 3 \frac{0^3}{3} x x = 72 72

s o so a n s w e r answer i s is 72 \boxed {72}

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.

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