Trajectory is the curve of a projectile in flight and affects flight distance. To find out which trajectory produces the longest rubber band flight, construct a rubber band launcher by gluing a spring-loaded clothespin to one end of a long narrow strip of wood. Cut two notches in the opposite end. Load the launcher by looping the rubber band through the notches and stretching it out and clamping it with the clothespin. Lay out a measuring line in a clear, open area and set the launcher at zero. Launch the rubber band by releasing the clamp. Use a protractor to launch at different angles for comparison. Measure and record the angle and flight distance.
Any excuse to race excites many fifth-graders, so a rubber band car just fills the bill. A cardboard square body with a wooden skewer axle and CD wheels makes a simple two-wheeled racer. Place one small catch on top of the cardboard body and another in the center of the axle and stretch a rubber band taut between them. Wind the axle several times to create potential stored energy and let it go to see kinetic energy in action.
For those that are more interested in flying things, a rubber band airplane will do the trick. Attach a nose hook propeller one end of a 12-inch by 3/8-inch balsa strip. Attach the a rubber band to the propeller's hook and lay it straight, but not stretched along one edge of the wood to determine where to insert a small eye hook to hold the other end. Build balsa frames for the wings, stabilizer and rudder. The stablizer should be a 4-inch by 2-inch rectangle; the rudder, a three-sided 2-inch by 2-inch square; and the wing, a 5-inch by 12-inch rectangle. Science Toymaker provides a template for constructing these pieces to the correct dimensions. Cover all the frames with tissue paper, trimming the edges flush with the wood. Hot glue the rudder perpendicular to the stabilizer in the center of the frame. Bend, but do not break the balsa in the center to form a V-shaped wing. Hot glue a balsa strip to the wing frame across the point of the V and a toothpick on both sides of this bar on both ends. Stabilize all joins with hot glue and tape the wing to the body. Find a large open area, wind up the propeller and watch it soar with the stored energy from the rubber band.
When spring or summer heat makes water toys a popular choice, try a rubber band boat. Cut a boat shape out of a block of polystyrene. Trim out a rectangular opening in the center for the paddlewheel. Press two small nails or tacks opposite one another into the foam at the center line of the opening. Cut two squares of 1/2-inch polystyrene sheets slightly smaller than the width of the opening. Notch them so they fit together in a cross shape. Stretch a rubber band around the wheel and loop around the posts at both sides. Cut a wheelhouse piece from the leftover polystyrene and glue to the top of the boat at the bow. If desired, paint the boat and seal with acrylic spray finish. Wind the wheel to power the rubber band and set sail.