Question

a needle 5cm long can rest on surface of water find weight of needle​

Answer 1

Answer:

0.07 n/m

I think this answer will help u

Answer 2

Weight of needle is 0.007 N

The given problem is related to surface tension.

Surface tension is defined as "the tendency of fluid surfaces to shrink into the minimum surface area possible."

Since, water will cover needle from two sides, thus total effective length will be 2l.

T = F/effective length

Surface tension of water is known - 0.07 N/m

Length of needle is - 5 cm = 0.05 m

Force = T*2l

Force = 0.07*2*0.05

Force = 0.007 N

Thus, weight of needle is 0.007 N.