Make your own flying rocket from 2-liter soda bottles. The rocket can be constructed from household items and, with a little help from a bicycle pump, it will shoot several feet into the sky. Building rockets is an engaging way to teach children about Newton's third law of motion, and they can have competitions to see whose rocket flies the furthest. The rockets are water-powered, making them far safer than explosive rockets.
Cut a strip of poster board to fit around the middle of the 2-liter plastic soda bottle. Use glue to secure it to the bottle.
Roll another strip of poster board up so it forms a cone and secure it with glue. Cut the bottom of the nose cone in a straight line. Make a ball of modelling clay that's 2 to 4 ounces in weight and press it into the inside tip of the nose cone. Attach the nose cone to the bottom of the 2-liter soda bottle. This will stabilize the rocket.
Cut out four fins in any shape you like. Glue them to the sides of the rocket near the top of the bottle pointed up. Duct tape the straw to the side of the bottle close to the top.
Drill a hole through the runner stopper big enough to fit the pump needle snugly. Use water to fill the bottle 1/4 to 3/4 of the way. Experiment with different volumes to see what works best for your rocket.
Place the rubber stopper with the needle in it into the bottle neck. Push the metal rod into the ground in the area where the rocket will be launched. Thread the metal rod through the straw until the bottle top and fins are resting on the ground.
Attach the bicycle pump to the needle and begin pumping. When the pressure is too great inside the bottle, the water will force its way out and the rocket will take off.