The initial velocity of a particle moving in a straight line is 10 \[m{{s}^{-1}}\]and the retardation is 2\[m{{s}^{-2}}\]. The distance moved by the particle in 5th second of its motion is
A)1m
B)19m
C)25 m
D)50 m
Correct Answer:
A
Solution :
[a] \[{{S}_{nth}}=u-\frac{a}{2}(2n-1)\] \[=10-\frac{2}{2}(2\times 5-1)\] \[=(10-9)m\] = 1 m