Question
A body covers 26, 28, 30, 32 meters in 10th,11th,12th and 13th seconds respectively. The body starts
A.
from rest and moves with uniform velocity
B.
from rest and moves with uniform acceleration
C.
with an initial velocity and moves with uniform acceleration
D.
with an initial velocity and moves with uniform velocity
Answer :
with an initial velocity and moves with uniform acceleration
Solution :
The distance covered in $$n$$th second is
$${S_n} = u + \frac{1}{2}\left( {2n - 1} \right)a$$
where $$u$$ is Initial velocity $$\& \,a$$ is acceleration
$$\eqalign{
& {\text{then}}\,26 = u + \frac{{19a}}{2}\,......\left( {\text{i}} \right) \cr
& 28 = u + \frac{{21a}}{2}\,......\left( {{\text{ii}}} \right) \cr
& 30 = u + \frac{{23a}}{2}\,......\left( {{\text{iii}}} \right) \cr
& 32 = u + \frac{{25a}}{2}\,......\left( {{\text{iv}}} \right) \cr} $$
From eqs. (i) and (ii) we get
$$u = 7\,m/\sec ,a = 2\,m/{\sec ^2}$$
$$\therefore $$ The body starts with initial velocity $$u = 7\,m/\sec $$
and moves with uniform acceleration $$a = 2m/{\sec ^2}$$