A meteoroid speeds up as it approaches Earth and its atmosphere because Earth's gravity pulls it in, increasing its velocity. The gravitational force becomes stronger the closer the meteoroid gets to Earth, causing it to accelerate as it falls toward the planet. This acceleration is due to the gravitational attraction between Earth and the meteoroid, which turns potential energy into kinetic energy, thus increasing the meteoroid's speed.

Additional details:

• Meteoroids are orbiting the Sun and when they come near Earth, they are pulled by Earth's gravity.
• Their speed as they enter the atmosphere can be very high, reaching up to about 72 km/s in some cases because they combine their orbital velocity around the Sun with Earth's orbital velocity.

In summary, the increase in speed of a meteoroid as it nears Earth is due to gravitational acceleration caused by Earth's gravitational field pulling the meteoroid closer and faster toward the surface.