phy graph

Denote:

x be the distance of the stone

t be the time

u be the initial velocity

a be the acceleration (negative in this case)

Final velocity, v = 0

By x = ut + 1/2 at2 ─── (1)

and v = u + at ─── (2)

From (2), u = 0 - at = -at ─── (3)

Sub (3) into (1):

x = -at2 + 1/2 at2

x = -1/2 at2

x/t = -1/2 at

Recall the equation of a straight line y = mx + c

We see that the graph x/t against t yields a striaght line.

The slope is -1/2 a, which is positive (Since a is negative)

Also, the straight line passes through the origin.

So, the answer is C.