Question

Velocity of a particle moving along positive $x$-direction is $V=(40-10t)m/s$. Here, $t$ is in seconds. At time $t=0$, the $x$ coordinate of particle is zero. The time when the particle is at a distance of $60m$ from origin :

• A. 2 s
• B. 4 s
• C. 6 s
• D. 8 s

Answer 1

Answer: (A), (C)

The correct options are
A 2 s
C 6 s

v=40-10t=$\frac{dx}{dt}$
Integrate to get, $x=40t-5t^2$ (c=0 because x=0 at t=0)
x=60 implies, $t^2-8t+12=0$. Solve the quadratic to get, $t=2$ and $t=6$