7.When I put the paper clip on the paper air plane, it has two action thrust, mass and little bit high gravity. But when the plane without the paper clip it make a thrust very fast because it light and has a low gravity. The distance is farther without the paper clip and shorter than have a paper clip on. My air plane's flight was straight and turn to upside-down when it land.
8.When I fly the air plane that go srtaight, flip and go up. When it land down to ground it turn to upside-down and land to the ground.
  In my plane design, I design my plane has a big wing to fly fast and little bit high. My plane has a nose but not too sharp. I want to make the plane light because I want it fly farther. I learn from investigation that more mass weight and gravity make the plane go down.