Question

For a particle moving according to the equation $x=a\cos \pi t$, the displacement in $3s$ is

• A. 0
• B. 0.5a
• C. 1.5a
• D. 2a
• E. a

Answer 1

Answer: (D)

Given, $x=a\cos \pi t$
Initially at $t=0$, then
$x=a\cos \pi (0)$
$\Rightarrow x=a$
Finally at $t=3$,
then $x=a\cos 3\pi$
$x=a\cos \pi$
$x=-a$
Total displacement $=2a$