Question

A body moving with uniform acceleration describes 12 m in the third second of its motion and 20 m in the 5th second. Find the velocity after 10 th second.

• A. 40 m/s
• B. 42 m/s
• C. 52 m/s
• D. 4m/s

Answer 1

Answer: (B)

42 m/s

Answer 2

${{S}_{n}}=u+\frac{a}{2}(2n-1)$ $12=u+\frac{a}{2}(2\times 3-1)$ ..(i) and $20=u+\frac{a}{2}(2\times 5-1)$ ..(ii) Subtract E (i) from E (ii) $8=\frac{a}{2}(9-5)=2a$ $\Rightarrow$ $a=4m/{{s}^{2}}$ From E (i) $12=u+\frac{4}{2}\times 5$ $u=2\,m/s$ Velocity $v=u+at=2+4\times 10$ $=42\,m/s$