motion

[muskan]

10

i think the answer should be 25 seconds. but the options don't have it.

[swansont]

Why do you think it should be 25 seconds? Show your work.

[Country Boy]

Look at it in terms of "5 steps forward and 3 steps back". That gains 5- 3= 2 m forward and take 5+ 3= 8 seconds.

[Sriman Dutta]

For the first question, total distance covered = length of train + length of bridge.

 

 

For the second one, draw a displacement time graph.

[LabRat1]

Ah 11th std NCERT were the good times....Check your displacement again.

[muskan]

He takes 55 steps forward and 30 steps backwards

[LabRat1]

He takes 55 steps forward and 30 steps backwards

 

Its not possible. A pit at a distance of 11m. Each step of 1m. 55-30=25, which means 25m. The dude definitely missed the pit according to your calculations.

[rosadaniels]

Why 25 and not 30?

 

Edited August 19, 2017 by rosadaniels

[Country Boy]

 First he goes forward to 5 m and then back to 2m.  That takes 8 seconds.  Then he goes forward to 7m and back to 4m.  That also takes 8 s so a total of 16 seconds.  Then he goes forward to 9m and back to 6 m.  That is now a total of 24 seconds.  Finally, he goes forward to 11m and falls into the hole.  That is a total of 29 seconds.

Edited August 19, 2017 by Country Boy