Question

An insect crawling up a wall crawls 6 cm up in first
second and then slides 4 cm down in next second. It
again crawls up 6 cm in third second and again
slides 4 cm downwards in 4th second. How long will
insect take to reach a hole in wall at a vertical height
of 24 cm from starting point?
0 20 S
O 27 s
O 25 S
0 19 s​

Answer 1

Answer:

19 sec

Explanation:

1st sec=6cm up

2nd sec = 4cm back

so in 2 sec net rise = 6-4= 2 cm up

so in 1sec net rise = 2/2= 1 cm up

but in the last sec it reaches 24 cm mark by crawling 6cm in that time, satisfying our question.

(so we don't consider it's crawling back after this.

in this last 1sec his net rise is 6 cm according to our consideration.)

now 24 -6 =18 cm

time taken to cover 18 cm= 18 sec

so total time= 18+ last 1 second = 19 sec