Newton's Universe?

Question

I did not fully understood the following sentences regarding gravity from "A Briefer History of Time" by Stephen Hawking. Would you explain it to me as clear as possible, thank you.

According to Newton's law of gravity, a body of twice the weight will have twice the force of gravity pulling it down. But it will also have twice the mass and thus, according to Newton's second law, half the acceleration per unit force ( by the way, what is half the acceleration per unit mean?). According to Newton's laws, these two effects exactly cancel each other out, so the acceleration will be the same no matter what the weight.

Answer 1

Weight and mass in this context are the same thing, the acceleration of gravity will be identical for any mass unless it is affected by air resistance. Read the article again and concentrate on what you read.

Answer 2

Pretty much, the force of gravity relates to the weight of both items involved (you and the earth). Something that's half as big as you has half the force pulling on it. This would suggest it would fall slower, since a smaller force is pulling it. However, snce Force=(mass)(acceleration) something twice as heavy with twice the force will balance out and have equal acceleration.

Answer 3

F = ma
Force (in Newtons) = mass * acceleration
'Half the acceleration per unit force' means exactly what it says. If you apply 100 N of force to a 100 kg mass, it will accelerate at 1 m/s². If you apply the same force to a mass of 200 kg, it will accelerate at .5 m/s²

Doug

Answer 4

Force = m a
also force acting on the body is its weight =mg
hence mg =ma1
thus a1=g

Now if you take an object twice its mass '2m'
Force acting on it =2mg
also since force =massXacceleration =2m a2
so 2mg=2ma2
hence a2=g

This a1=a2

Answer 5

This explains why when you drop a hammer and an anvil, they fall at the same rate. There is more attraction between the anvil and the earth, but the anvil also has more inertia to overcome. So they fall at the same rate.

Answer 6

This book is a spoof or a joke on the real book, not meant to be taken seriously.
Look at the full title, the last words are "A Parody" if you look up parody you'll find your answer.