Though I saw a screenshot off facebook the other day where the poster said that all life on Earth would bake if we orbited ten feet closer to the sun.....
Once I was walking towards a set of sliding doors. I noticed them open and close for a group of people walking ahead of me, but when I came to them they wouldn't open. Judging that the sensors weren't sensitive enough to detect my modest weight, I decided to leap vertically in the air in the hope that when I came down the extra force of my impact would open the doors. It did not, and couldn't have done.
Why not?
Because it employed an optical sensor and not a pressure one.
. If the rope is longer so the marine can put the rope at an angle by walking a few feet away from the grandpa he can lift the grandpa if he is strong enough
Not if he's standing on ice... There's gonna be a horizontal component to the force that the friction between his feet and the ground will have to overcome.