Phun with Physics

Warning!- Adult supervision: choking hazards & liquids not for drinking.

Materials

Balancing Bird

· 4 pk. crayons

· 2 washers

· Washi tape

· Scissors

· Template

CD Top

· CD

· Clay

· 3D printed top

· Stickers

Walking Horse

· Template

Self-Propelled Car

· Plastic jar

· Tongue depressor

· Small rubber band

· Paperclip

· Washer

Oscillating Woodpecker

· Straw

· Template

· Rubber band

Procedure

Balancing Bird

1. Cut along the outline of the balancing bird template.

2. Try to balance the bird on your hand by placing the beak on your finger. Are you able to balance it?

3. Now tape a metal washer to the end of each wing. Are you able to balance the bird now?

4. Use the crayons to color your balancing bird!

CD Top

1. Place the CD with the shiny side up over the 3D printed top so that the handle goes through the hole in the CD.

2. Press the clay around the handle of the top so that it is secured to the CD.

3. Your CD top is complete! Decorate the CD using the stickers provided.

Walking Horse

1. Cut around the rectangular outline of the walking horse template, then cut the dotted lines.

2. Fold the legs down. Fold the tail and head upwards. Roll the tail so that it curls, and fold the end of the head down.

3. Using the centimeter (cm) ruler on your STEM SAK bundle box, measure 3 millimeters (mm) from the end of each leg on the outside edge and mark it. Cut from the mark to the inside corner of each leg to create a slight angle (see video for clarification).

4. Hold up one end of a book or piece of cardboard to create a gentle incline. Place your horse at the top with the head facing down the slope. Let go of the horse and experiment with the angle of the slope so that it ‘walks’ down the incline.

Self-Propelled Car

1. Open the plastic jar—thread the rubber band through the hole in the bottom of the jar and secure it on the outside of the jar using the rubber band. Tape the paperclip down using the washi tape.

2. Thread the other end of the rubber band through the hole in the lid and then through the washer—place the rubber band around the tongue depressor. Place the lid back on the jar.

3. Cut the tongue depressor so that it is slightly longer than the diameter of the jar.

4. Rotate the tongue depressor several times– place your car on the ground and watch it go!

Oscillating Woodpecker

1. Cut out the woodpecker template along the solid lines. Tape the wings to the body of the bird. Color the bird using the crayons.

2. Fold the bird along the dotted line—place the straw inside the crease and cut it to the length of the bird. Secure it with washi tape.

3. Tape the bird together with washi tape.

4. Cut the rubber band. Thread it through the straw.

5. Holding both ends of the rubber band, stretch it out and hold it vertically with the woodpecker at the top. The woodpecker should peck (or oscillate) as it slowly moves down the rubber band.

Science Behind it!

Balancing Bird

When you try to balance the bird on your finger before taping the washers to the wings, the bird’s center of mass (or center of gravity) is too far back for the bird to balance, so it falls off of your finger. The center of mass of an object is the point where all of the mass is evenly distributed. Taping the washers to the ends of the wings shifts the center of mass forward to the bird’s beak. Try to balance the bird on a pencil or the corner of a table! Where else can you balance your bird?

CD Top

When you spin a top, you are converting potential energy (energy at rest) to kinetic energy (energy in motion). The force that keeps a top spinning is called angular momentum. Newton’s 1st law states that an object in motion stays in motion (unless an outside force is acting on it)—this law along with the principle of conservation of angular momentum is why a top spins for such a long time. However, external forces such as friction and gravity act on the top which slows it down over time—though friction is minimized due to the tiny surface area of the point of the top that rests on the surface that it is spinning on.

Walking Horse

When the horse is at the top of the incline, it has a lot of potential energy. When you release the horse, potential energy is changed into kinetic energy and it begins moving down the ramp. If the incline is too steep, the horse will just slide down, but if the incline is shallow enough, friction will prevent it from sliding and it will instead wobble back and forth and “walk” down the incline. Experiment with different angles for the incline to determine which angle causes the horse to move the fastest without sliding!

Self-Propelled Car

When you twist the rubber band, you are adding kinetic energy which is converted to potential energy stored in the rubber band. When you set the car down, the potential energy is converted back into kinetic energy as the rubber band untwists. This causes the tongue depressor to exert force onto the ground. Newton’s 3rd law states that when an object exerts a force on another object, the other object exerts an equal and opposite force. This equal and opposite force propels the car.

Oscillating Woodpecker

When the woodpecker is at the top of the rubber band, it has potential energy. Gravity and kinetic energy pull the woodpecker down the rubber band, but friction between the straw and the rubber band prevents it from sliding, causing it to oscillate.