# 1D Motion Question

1. Aug 8, 2012

### mttal24

1. The problem statement, all variables and given/known data
Give example of a motion where x>0, v<0, a>0 at a particular instant.
x-->Position
v-->Velocity
a-->Acceleration

2. Relevant equations
I thought I had to give an example such as a car, ball etc.
x(t) ie; position for time t; given by
x(t)=A+Be$^{-\gamma t}$
where A>B, $\gamma$>0 are chosen +ve constants.

3. The attempt at a solution

2. Aug 8, 2012

### bigerst

the given example wasnt the only solution

another example would be
x(t) = 3t^2 -20t+100 at t=2

for your example use calculus, for at t=1, x>0 as u can check
differentiate dx/dt = -γBe^(-γt), which is less than zero at t=1
differentiating again gives a=(γ^2)(B)(e^-yt) which is positive at t=1