Q. A body moving with uniform acceleration, describes 40 m in the first 5 s and 65 m in next 5 s. its initial velocity will be
A) $4\ {ms}^{- 1}$
B) $2.5\ {ms}^{- 1}$
C) $3\ {ms}^{- 1}$
D) $11\ {ms}^{- 1}$
Explanation
(c) Here, $s_{1} = 40\ m,\ s_{2} = 65\ m,$
$\ \ \ \ \ \ \ \ \ \ \ \ t_{1} = 5\ s,\ \ \ \ a = ?$
$\ \ \ \ \ \ \ \ \ \ \ \ \ a = \frac{s_{2} - s_{1}}{t^{2}} = \frac{(65 - 40) \times 2}{(5)^{2}}$
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ = \frac{50}{25} = 2\ {ms}^{- 2}$
Now, $s_{1} = ut + \frac{1}{2}\ at^{2}$
$\ \ \ \ \ \ \ \ \ \ 40 = 5u + \frac{1}{2} \times 2 \times 25$
Or $\ 5u = 15\ \ or\ \ u = 3\ {ms}^{- 1}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.