Question

A particle moves along x-axis in such a way that its coordinate x varies with time t according to the expression, $x=2-5t+1.25t^2$. The initial velocity of the particle is?

• A. $-5$ m/s
• B. $-3$ m/s
• C. $3$ m/s
• D. $6$ m/s

Answer 1

Answer: (A)

$-5$ m/s

Displacement x varies with time 't'$=2-5t+1.25t^2$

We know velocity v$=\frac{displacement}{time}$

So,differentiating displacement x with respect to time we get

$\frac{dx}{dt}=-5+2\left(1.25\right)t$

At time = o seconds initial velocity = -5 m/s.

(as change in displacemet with respect to time gives us velocity)