A particle is confined to move along the x-axis between reflecting walls at x = 0 and x = a . Between these two limits it moves freely at constant velocity v . If the walls are perfectly reflecting , then its displacement time graph is -

Options

A.
B.
C.
D.

Answer

A

Explanation

When it move 0 to a
`v = (x_(2) - x_(1))/(t) = (a-0)/(t) x_("max") = a `
x = vt , v = const so `x prop t " " ...... (i) `
when it move 'a' to 0
`v = x_(2) - x_(1) = (0 - a)/(t) x_("min") = 0 `
v' = -v constant , `(dx)/(dt) = -v " " ......(ii)`
so both of condition will be satisfy through option (1).