# Is the speed of sound modelled by a linear equation?

A cannonball is launched from a point 100 m above ground, at a speed of 20 m/s. This is modelled by the equation $$h(t)=-4.9t^2 +20t +100$$

The speed of sound (of the cannonball is) 380m/s

If a person sitting directly underneath the cannonball runs as soon as they hear the sound do they escape the cannon?

My main question is "$$y=-380x+100$$" the correct equation to model the cannon's sound?

So the front of the sound wave is modeled by $$y=-380t+100$$ which means, at ground level, the sound can be heard at 0.26315 seconds. But the cannonball reaches ground at around 7 seconds. So the person can escape.