Question

A body moving with uniform acceleration travels a distance $s_n$= (0.4n + 9.8) m in $n^{th}$ second. Initial velocity of the body is (in $m{s}^{-1}$)

• A. 0.4
• B. 10
• C. 3.5
• D. 4

Answer 1

Answer: (B)

10

$s_n$ distance travelled in n sec-distance travelled in (n-1) sec

$s_n=(u_{1}n+\frac{1}{2}a{n}^2)-\left(u_1\right(n-1)+\frac{1}{2}a(n-1{)}^2)$

$=u_1+\frac{1}{2}a(n^2-(n-1{)}^2)$

$=u_1+\frac{a}{2}(+2n-1)=u_1+an-\frac{a}{2}$

Comparing with: $s_n=0.4n+9.8$

$a=0.4,u_1-\frac{0.4}{2}=9.8$

$u_1-\frac{0.4}{2}=9.8$

$u_1=10m/s$