How fast does the Falcon 9 travel?

The Falcon 9 lifts off with nine Merlin engines producing about 7,600 kN of thrust at sea level, just a bit more than needed to lift its 549 t. That's why the first seconds are slow, and the rocket takes nearly a minute to break the sound barrier. Around two and a half minutes in, the first stage shuts down at about 70 km altitude and roughly 8,000 km/h; on missions with recovery, SpaceX cuts it off earlier to save propellant. After separation, the second stage's single vacuum-optimized Merlin engine burns for six more minutes until the payload reaches 7.8 km/s, around 28,000 km/h, the speed that keeps it in orbit at about 200-500 km.

The first stage flips over, and on missions returning to shore it performs a boostback burn that reverses its trajectory. On reentering the atmosphere at more than 4,000 km/h, a three-engine burn slows it down so the grid fins can steer it. One final burn, with a single engine, takes it from supersonic speeds to zero in under half a minute, over the drone ship or the landing pad on land. This profile is what allows the same stage to fly dozens of times.

When the destination is geostationary transfer orbit, the second stage keeps pushing to about 10.2 km/s, raising the apogee to 35,786 km. For interplanetary probes, like NASA's DART, the Falcon 9 has placed the payload on an escape trajectory, above 11 km/s. On the most demanding missions SpaceX gives up recovering the first stage, because every kilogram of propellant reserved for landing takes speed away from the payload.