A body starts from rest. What is the ratio of the distance travelled by the body during the 4th and 3rd second?
A
7/5
B
5/7
C
7/3
D
3/7
Step-by-Step Solution
Method 1: Galileo's Law of Odd NumbersFor a particle starting from rest with uniform acceleration, the distances traversed during equal successive intervals of time are in the ratio of odd numbers: 1:3:5:7:9… . Distance in 1st second ∝1Distance in 2nd second ∝3 Distance in 3rd second ∝5Distance in 4th second ∝7 Therefore, the ratio of the distance travelled in the 4th second to that in the 3rd second is 7:5 or 7/5.
Method 2: Kinematic FormulaDistance travelled in the n-th second is given by Sn=u+2a(2n−1). Since the body starts from rest, u=0.
S4=2a(2×4−1)=27a.S3=2a(2×3−1)=25a.
Ratio S3S4=5a/27a/2=57.
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