Activities to Try at Home: 3
Here are some try-at-home demonstrations from the Shell Questacon Science Circus.
The Collision Show
Colliding balls, superballs and putty help to show how the surface of an object and energy are important for crash, boom, bang demonstrations.
Bouncing Superballs
Superballs can be a lot of fun because they are different to a normal rubber ball.
Try throwing your superball so that it bounces from the floor to the underside of a table or flat piece of board held by someone else. Try the same thing with another type of ball, such as a golf ball.
What happens?
The superball behaves a little strangely! Instead of bouncing all the way through to the other side, the superball will bounce back to you!
Why?
To help answer this, try holding the superball in your fingertips and rubbing it along a smooth, dry surface such as a glass table top. Did you find that the superball strongly grips the surface?
Although the surface of the superball looks smooth, the rubber molecules which make up the superball show a large amount of friction when the ball contacts another surface. This makes the superball behave as if it has a very rough surface. The superball is also very elastic. This means that when it collides with something most of the energy is converted into the rebound movement, and so superballs are very bouncy!
Collision Car
Another interesting demonstration in the collisions show is the car crash. The car crash car is one that can be made by anyone at home.
You will need
- 1 shoe box
- 4 flat cardboard wheels
- 6 pieces of wire
- 1 marker
- some aluminium foil
- some cling wrap
- some sticky tape
What to do
The shoe box will be the car body. Read steps 1-3 before beginning.
- On the front of the box wrap around a piece of aluminium foil which will be the crumple zone for the front of the car.
- Fold the foil over at the front so the front of the car looks solid, but leave the underbelly open so that you can put your fingers under this and push the foil back out after a crash.
- The foil should stick out about 8 cm when it is folded. Using some sticky tape to hold the foil together.
- Repeat this for the back of the car.
- On the top of the car draw a 10 x 10 cm square. Place wires about 10 cm high in each corner of the square. Make these stable by sticky taping the bottom of the wire to the underside of the box.
- Wrap the wire with aluminium foil to make it stronger. Over the top tape a sheet of foil which will be the roof.
- Around the side of the wires wrap cling wrap which will be the windows.
- Run two longer pieces of wire through the sides of the car, which are the axles for the car. Attach to each side a cardboard wheel which has a hole in the centre for the wire to be threaded through. Bend the wire over so that it will not come back out of the wheels.
- Draw on a licence plate and windows with the marker, also add some headlights if you like.
You now have your own crash car, which can be increased and used again after each crash.
Balancing The Improbable
It”s something we do every day and take for granted — balance! See how to balance familiar and unusual objects, find the centre of mass and why friction is important.
Balancing broomsticks
This is an easy experiment you can do by yourself. All you need is a long object like a broomstick, mop, ruler, golf club or an ordinary stick.
Hold your hands out in front of yourself with your palms facing each other and your thumbs pointing towards the sky. Balance the object between your thumb and index finger, making sure you are not holding the object with your thumb. At this stage your hands should be spread apart so they are supporting the object at its ends. Now move your hands showly together as if you were clapping in slow motion. Try not to move your hands quickly.
Where your hands meet is the object's balance point — the point at which the object can be balanced. Try balancing it using only one finger
Did you notice that your hands did not move together? First one hand slides then it comes to rest then the other moves. This is because of a force called friction. Friction acts between the skin of your fingers and the object.
To see this effect better, start with both hands at the balance point with your thumbs up and palms touching each other. Now try and move your hands away from each other towards the ends of the object. Did only one hand move? The hand that does not move is closer to or at the balance point and so is carrying most of the object's weight. This hand is harder to move because there is more friction. It is like when you press your hands together really hard and then try to slide one over the other — it's very hard to do because there is more friction between your hands than if you only had your hands pressed lightly together.
The Slime Show
Gooey, ooey — that's our slime. We look at what fluids are like in our everyday life and learn about viscosity and elasticity.
Viscosity Race
During the slime show, we do a thought experiment to demonstrate the viscosity of normal fluids. Imagine a glass of water in one hand and a glass of honey in the other. Pour them at the same time to see which one lands first. You can also have a real race between different fluids.
WARNING! this is a messy experiment. Do it outside or make sure that the work area is covered with newspaper.
You will need
- 3 drinking glasses
- 3 dinner plates
- 3 people
- pencil or whiteboard marker
- water
- cooking oil
- honey
What to do
- With the pencil or whiteboard marker, mark a starting line on one side and a finish line on the other side of each plate.
- Place a tablespoon (20 ml) of water, cooking oil and honey in separate glasses.
- Give 3 people a glass each. Tip the glass onto its side on the dinner plate, making sure that the rim of the glass is on the starting line. Which fluid wins the race?
What happens?
Viscosity is a measure of how easily a fluid flows. The word comes from the Latin for ‘sticky’. The three fluids have different viscosities. The viscosity of a normal fluid can change according to temperature. Try heating or cooling the fluid before the race! You should find that the viscosity decreases when you increase the temperature.
The Music Show
Make your own beautiful music using coathangers, cups, buckets and other things. Why are vibrations important?
Musical Coathanger
This demonstration shows how sound travels differently through solids compared to air.
You will need
- a wire coathanger
- two 1m long pieces of string
- a ruler
What to do
- Tie a piece of string to each corner of the coathanger.
- Tie the other end of each string to the index finger of each hand.
- Lean over and (carefully!) place the fingers with the string on them into your ears. Let the coathanger swing freely.
- Get someone else to tap the coathanger with the ruler.
- Listen for the loudness and length of the sound.
- Now get someone else to try it and listen to the sound.
What happens?
With the musical coathanger in your ears the sound you hear is much louder and longer than without it in your ears. The sound made when you hit the coathanger travels through the string and your fingers to your ears much better than it travels through the air. Try placing your ear on a table and hitting the table and you will notice that sound travels much better through solids than through air.
