somethng to do with mechanics??????

Question

2 men each of mass 80 kg and a woman of mass 64 kg are walking on a horizontal path which forms an edge of a lake.the woman s expensive hat is blown into the lake and is caught by reeds at a distance of 4 metres from d path.a rigid plank,of lenghth 6 metres and whose weight can b ignored is availablle for use in retrieving the hat by alowing it 2 rest on the path while overhanging the lake woth 2 ppl standing on the part of the plank which is in contact with the path and the third person effecting the recovery..determine whether (A) one of the men can effect the recovery...(B) the woman can effect the recovery?? Reply

Answer 1

G ~ 10m/s^2

The torque of a man on the end retrieving the hat would be 80 * 10m/s^2 * 4m = 3200 Nm

The torque of the woman and the man on the shore side would be (80+64) * 10 * 2 = 2880.

This would not work.

The torque of the woman on the end retrieving the hat would be 64 * 10m/s^2 * 4m = 2560 Nm

The torque of the two men on the shore side would be (80+80) * 10 * 2 = 3200.

This would work.

Answer 2

2 m of plank are in contact with the path as the hat is 4m away.

Suppose woman goes to get the hat, and men stand on the plank.

Taking torque about the edge of path.
Under limiting condition,
Clockwise torque=anticlockwise torque

=>64*4=80*2 + 80*2

=>256=160 + 160
=>256<320

=>Woman can go to retrieve the hat.

If one of the men go

80*4=64*2 + 80*2

=>320>288

So the man can't go as the plank will rotate about the edge and fall in the lake.

Answer 3

use the plank, to pull the hat from the reeds to shore.