## Explanation

### Explanation of Gravity and Inertia Working Together

Gravity is the attractive force that pulls all objects towards one another, while inertia is a property of matter that resists changes to its state of motion.

### Combined Effect on Motion

The interplay of gravity and inertia **keeps celestial bodies in orbit**. Gravity pulls objects towards the center of a gravitational field, whereas inertia wants objects to continue in a straight line. This balance creates elliptical orbits.

Here:

$\mathbf{F_g}$is the gravitational force,

$G$is the gravitational constant,

$m_1$and

$m_2$are the masses of the objects, and

$r$is the distance between the centers of the two masses.

### Resulting Path

Because of inertia, an object will **continue to move in a straight line** unless acted upon by another force. Gravity continuously acts as that force, pulling the object towards another body and **preventing it from moving away in a straight line**. This creates the curved paths we observe, such as planets orbiting stars.

### Key Formula

The law of inertia as part of Newton's first law can be described as:

$\mathbf{F} = m \mathbf{a}$Where:

$\mathbf{F}$is the net force acting on the object,

$m$is the mass, and

$\mathbf{a}$is the acceleration.

### Summary

**The interaction between gravity and inertia** changes the motion of objects, creates orbits, and prevents objects from continuing in a straight line in space. This delicate balance dictates the structure and dynamics of our universe.