Re: Would the earth move if enough force is applied?

Date: Tue Sep 22 11:06:58 1998
Posted By: Pauline Barmby, grad student, Harvard University Astronomy Dept.
Area of science: Physics
ID: 906215230.Ph
Message:
```
Rene - the earth's orbit wouldn't be affected by everyone in China
jumping off a chair at the same time. Sorry - it's a fun idea.

Let's work this out quantitatively.
Suppose when you hit the ground you hit with a force equal to
twice your weight. Let's assume that the average mass of a Chinese
person is 60 kg, and that there are 1.2 billion people in China.

Total force on the Earth:
(60 kg) x (9.8 m/s^2) x 2 x (1.2 X 10^9 people) = 1.41 x 10^12 N

Acceleration of the Earth this this force produces:
a=F/m(Earth) = (1.41x10^12 N)/(6.0X10^24 kg) = 2.4 x 10^-13 m/s^2.
This is very very small.

For comparison, let's calculate the acceleration of the Earth
due to the gravity of the Sun, which is what keeps the Earth in
its orbit:

a=F/m(Earth)=GM(Sun)/r^2
a = (6.67X10^-11 N m^2/kg^2) x (2.0 x 10^33 kg)/(1.5 x 10^11 m)^2
a = 5.9 x 10 ^-3 m/s^2
This is also a pretty small acceleration but it's a lot larger than
what you could get from people jumping off chairs!

Pauline

```

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