# About how fast is an asteroid going when it hits a planet?

Dec 12, 2015

Probably rather variable, but of magnitude similar to $50 , 000$ meters per second.

#### Explanation:

I think it would be quite variable depending on the circumstances, but similar in order of magnitude to the speed with which the Earth orbits the sun.

Let's do a few rough calculations:

The Earth is roughly $9.3 \times {10}^{7}$ miles from the sun

So the length of the Earth's roughly circular path around the Sun is about $2 \pi$ times this, say $5.84 \times {10}^{8}$ miles.

The Earth travels this path in about $365$ days, so the miles per day is about $\frac{5.84 \times {10}^{8}}{365} = 1.6 \times {10}^{6}$ miles per day.

Divide by $24$ to get miles per hour: $\frac{1.6 \times {10}^{6}}{24} \approx 67 , 000$ miles per hour

To get meters per second multiply by $\frac{1609.344}{3600}$ to get about $30 , 000$ meters per second.

Compare this with the speed at which comet Shoemaker-Levy collided with Jupiter, which is estimated at $60 , 000$ meters per second. So it seems we're in the right ballpark.