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2.Motion in Straight Line
medium
A body is moving with a uniform acceleration covers $40\,m$ in the first $4\,s$ and $120\,m$ in next $4\,s.$ Its initial velocity and acceleration are
A
$0,\,\,5\,m/s^2$
B
$2\,m/s,\,\,5\,m/s^2$
C
$4\,m/s,\,\,10\,m/s^2$
D
$4\,m/s,\,\,5\,m/s^2$
Solution
$A$ to $\mathrm{B}: 40=\mathrm{u} \times 4+\frac{1}{2} \mathrm{a} \times 4^{2}$
$40=4 u+8 a$ $…(i)$
$A$ to $\mathrm{C}: 40+120=\mathrm{u} \times 8+\frac{1}{2} \mathrm{a} \times 8^{2}$
$160=8 u+32 a$ $…(ii)$
Solving $( i )$ and $(ii),$ we get
$\mathrm{u}=0, \mathrm{a}=5 \mathrm{m} / \mathrm{s}^{2}$
Standard 11
Physics
