A) 64m
B) 64cm
C) 640cm
D) 0.064m
Correct Answer: C
Solution :
Key Idea: When a body starts from rest its initial velocity is zero. Using 2nd equation of motion, we have \[s=ut+\frac{1}{2}a{{t}^{2}}\] where, s is displacement undergone, u is initial velocity, a is acceleration due to gravity and t is time Since, body starts from rest, so u = 0 Here, \[a=20\text{ }cm/{{s}^{2}},\text{ }t=8\text{ }s\] \[\therefore \] \[s=0+\frac{1}{2}\times 20\times 8\times 8=640\,cm\]
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