# Fun Physics Experiments with Household Objects

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Build a rocket, make a bottle invisible, polarize light, silence a blaring radio. The experiments in this sample chapter demonstrate some of the basic laws of physics, and require only household items to accomplish.
This chapter is from the book

## Rockets with Chemical and Air Propulsion

Let's build a cool rocket and its launch platform from scratch.

### Step By Step

Supplies

• vinegar

• baking soda

• empty film canister with lid

• construction paper

• superglue

Put a small amount of baking soda and some vinegar (figure out for yourself the proportions that work best) in the film canister and cover it quickly. The lid of the film canister is the bottom end of your rocket. Stand back and get ready for blast-off! You can improve your rocket by adding a conic nose and fins made of construction paper to it, as done in the next model (air propulsion).

WARNING

Be sure you choose a launch site that will not be damaged by the vinegar and baking soda!

### A Step Further

There is a slightly more sophisticated way to engineer your rocket. Mix the baking soda with water to form a paste that will stick inside the lid of the film canister even when you hold it upside down and put it on the canister. Calculate the right amounts, spread the baking soda inside the lid, and place the vinegar in the canister. Put the lid on the canister, keeping the canister upright. When you are ready for launch, turn the canister upside down and place it on the launch site. Watch it go!

Can you think of other ways to engineer a vinegar and baking soda rocket?

Fun Facts

In the case of the chemical propulsion, vinegar, an acid, and baking soda (sodium bicarbonate) mixed together produce carbonic acid, which quickly decomposes into carbon dioxide (CO2) and water. As the CO2 expands, it makes the rocket (canister) move up. The rocket is hit by the CO2 molecules moving up and, in turn, it kicks them back. It is the action = reaction principle at work.

### Step By Step

Supplies

• construction paper

• 3.3 ft (1 m) piece of ridged hose

• 9 in (22 cm) piece of PVC pipe in which the hose can be fitted tightly

• 2-quart (2-liter) plastic bottle (you can also use 1-gallon bottle)

• piece of wood (base), roughly 4 x 10 in (10 x 25 cm), 5/8 in (1.5 cm) thick

• wood stick, roughly 1 x 1 x 8 in (2.54 x 2.54 x 20 cm)

• 1 nail

• 1 screw with washer

• piece of wire

• disk, 1 1/4 to 2 in (3 to 5 cm) radius, or a drawing compass

• white glue

• small Styrofoam ball (optional)

The Platform

With a hacksaw (or other saw), cut off a piece of the wood stick. Attach the stick laterally to the base with two nails, as shown in the figure. Insert one end of the hose into the tube until it reaches the tube's end. Drill a hole all the way through from one side of the tube to the other to pass the screw. Use the screw to fasten the tube to the wood stick. Insert the other end of the hose into the bottle (if necessary, use masking tape around the tube's ends to keep the hose tightly fitted).

The Rocket

Make an 8 in (20 cm) long cylinder out of construction paper, which fits tightly in the PVC pipe. Draw on the construction paper a 1 1/4 to 2 in (3 to 5 cm) radius semicircle, using the disk as a guide, or use the drawing compass. Cut out the semicircle and make a cone out of it that fits the cylinder. Attach the cone to the top of the cylinder with masking tape. Alternatively, you can use a Styrofoam ball as the nose of the rocket. Just fit it in the top end of the cylinder (using glue or masking tape to fasten it to the body of the rocket). Cut out three rectangular triangles with roughly 1 3/8 in (3.5 cm) base and 2 in (5 cm) height for the three fins. Fold 1/4 in (0.5 cm) of the border of the triangles (see figure) and attach them to the rocket's body at the places indicated. The fins can be positioned either vertically or slightly tilted (around 20º). To launch the rocket, just put the bottle on the ground and stomp on it with one foot. You can try different rocket designs to see which achieves the highest point. You can also tilt the platform and discover at which angle the rocket reaches the maximum distance on the ground. After each launching, the plastic bottle deforms. To restore it, you have to blow through the top end of the PVC pipe. Eventually, you will have to replace the bottle and make a new rocket.

Fun Facts

The air flow kicks the rocket up, and the rocket in its turn kicks the air back. This is just the action = reaction principle at work. Can you recognize here the same principle of the previous rockets? The fins of the rocket also play an important role, as they do for sharks and other fish. When the fins are tilted, they make the rocket spin around its axis. When you ride a bicycle, you don't fall because the spinning wheels give it a special stability. (See Experiment 35, "The Bicycle's Trick") The same holds for the turbines of the jet engines of an airplane. What about the rocket?