Question

1. Is it true that as a penny drops to the ground that it exerts a gravitational force on the earth? If so, then why do we not notice the earth move toward the coin?

2. Jim and Ellen are astronauts floating some distance apart in space. They are joined by a safety cord whose ends are tied around their waists. If Jim starts pulling on the cord, will he pull Ellen toward him, or will he pull himself toward Ellen, or will both astronauts move? Explain.

Answer 1

1.

According to Newton's law of gravitational force every body which has mass exerts certain amount of force of another body which has a mass, the force is given by

$F=\frac{G*M1*M2}{R^{2}}$

Where G=gravitational constant

M1= mass of earth

R = radius of earth

Substituting we get the value 9.81 m/s²

I.e g values

So F =mg

But that force is very small compared to the mass of the earth and also the force between earth and sun system

That is the reason why the penny will not move earth. But it certainly exerted some force which is very small.

2.

Since there is no gravity in space when Jim pull the cord with some force the same force is exerted on him by the cord according to Newton's third law of motion(action=-reaction)

So both the astronauts move towards one another