# HElp Physics problems

1. Feb 25, 2005

### o04jjang

HElp Physics problems....ASAP!!

Four 1,000,000- kg masses are arranged in a square, 74meters on a side. To the nearest ten thousandth of a Newton, what is the magnitude of the force the mass in the lower left hand corner?

If the Earth's period is 365.25 days and its distance to the (center of the) Sun is one astronomical unit (AU), what is the period, to the nearest day, of an asteroid in a circular orbit about the Sun with a radius of AU?

2. Feb 25, 2005

### learningphysics

You've got 3 vectors... The force due to the top left hand mass on the lower left hand mass. The force due to the top right hand mass on the lower left hand mass. And the force due to the left right hand mass on the lower left hand mass.

I'd do it this way. Get the total vertical component of the force on the lower left hand mass first. That means the force due to the top left hand mass (which is vertically downward) with the VERTICAL component of the top right hand mass (so you'll need a little trigonometry here).

Then I'd get the total horizontal component. That means the force due to the bottom right hand mass (which is horizontal leftward) along with the HORIZONTAL component of the top right hand mass.

The two components are the same value... by symmetry. So you can actually just get the vertical, and then you know the horizontal is the same thing.

When you've gotten the two components, use the pythagorean theorem to get the total magnitude.

Is the radius of the asteroid's orbit also 1 AU? You just wrote radius of AU but I want to make sure you didn't mistype.

Last edited: Feb 25, 2005