Question

At what time instance t, the particle's displacement is positive but particle's velocity negative

• A. t = 2 sec
• B. t = 10 sec
• C. t = 17 sec
• D. t = 30 sec

Answer 1

The correct option is C

t = 17 sec

Let's check all options:

At t = 2 displacement is positive or graph is above x-axis

$Velocityis\frac{changeindisplacement}{timetaken}$

$\therefore Theparticl{e}^{\prime }sdisplacementisincreasing$

In other words particle is going away from origin

So for this portion final - position initial will be positive

$d_f-d_i=△d=positive$

$Velocity=\frac{△d}{△t}=positive$

At t = 10 sec the particle position is positive but what about its velocity. The particle position is not varying for quite some time.

$Velocity=\frac{△d}{△t}=0$

At t = 17 sec displacement positive as graph above x-axis.

Velocity = $\frac{△d}{△t}$ = negative

At t = 30 position itself is negative.