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Motion In Straight Line

Question
CBSEENPH11017003

A drunkard walking in a narrow lane takes 5 steps forward and 3 steps backward, followed again by 5 steps forward and 3 steps backward, and so on. Each step is 1 m long and requires 1 s. Plot the x-t graph of his motion. Determine graphically and otherwise how long the drunkard takes to fall in a pit 13 m away from the start.

Solution
Length of 1 step taken by drunkard = 1 m

Time to take 1 step = 1 sec 

So, the speed of the drunkard = 1 m/s 

When he walk 5 steps forward, its position is 5m at time 5s.
After walking 3 steps backward, the position of drunkard at 8 sec becomes 2m. 

Time, t (sec) Distance, x (m)
5 5
8 2
13 7
16 9
24 6

So, the position- time graph is as shown in figure.