Candle seesaw
question
Why can the seesaw go up and down?
Scientific basis
Lever principle:
The magnitude of the two forces acting on the lever is inversely proportional to their arm.
That is, power× power arm = resistance× resistance arm.
scientific explanation
People's pressure on the seesaw is power and resistance respectively.
The distance between man and the fixed point of the seesaw is the arm of force,
The seesaw is an equal arm lever, and both sides are "evenly matched" to maintain balance.
simulation experiment
Use two candles as two arms of the lever, light the candles,
You can see the "candle seesaw" with flames, which keeps swinging up and down.
Experimental materials and tools
(1) A long rope.
(2) Fix both ends of the long rope with two high-back stools.
(3) Hang the drinking straw (thicker) on the long rope.
(4) toothpicks, inserted in the straw, are used to generate the fulcrum of the seesaw and fix the candles.
(5) Two birthday candles are used as the two arms of the seesaw.
(6) lighter.
(7) Scissors and adhesive tape.
experimental procedure
The first step is to cover the long rope with straw, just like the experiment above.
Step 2: Tie both ends of the long rope to the high-back bench.
The third step is to insert a toothpick into a straw (thicker).
Put it in from one side of the straw, through the straw and out from the other side.
Keep an eye on it, but be steady.
Pay attention to safety, toothpicks are sharp, so be careful with your hands.
In this way, the "fulcrum" of the seesaw is made, and the two ends of the toothpick are used to fix the candle.
Step four, put two birthday candles on tape paper.
Respectively adhered to both ends of the toothpick.
The length of birthday candles should be consistent, which is equivalent to "equal arm bar"
Look, the candle seesaw has taken shape.
The fifth step is to light the candle and find that the two ends of the seesaw are balanced at this time.
If the candle at one end burns faster and drops a tear,
The candle at this end has sunk.
Because the sinking end is in full contact with the candle flame, the burning speed is accelerated.
The candle is short, the weight is reduced, and it has to be tilted, so the other end sinks.
In this way, the "candle seesaw" rises and falls happily.
How about this experiment? Is it simple and interesting?
Balloon rocket launch
question
Why can Chang 'e II satellite be sent into space by Chang 'e III carrier rocket?
Where does the rocket power come from?
Scientific basis
Newton's third law:
The action and reaction between two objects are always equal in size and opposite in direction.
Acting on the same straight line.
scientific explanation
When the rocket is launched into the air, the gas released by fuel combustion is forced to spray downward.
These gases in turn exert an upward reaction force on the rocket.
Under this power, the rocket took the satellite into the sky.
5.5 hours before the launch of the rocket, the rocket was filled with liquid hydrogen at low temperature.
In order to ensure the power of the rocket, the refueling work has been maintained until the last two minutes before launch.
simulation experiment
Loosen the mouth of the inflatable balloon, and the air in the balloon will be ejected backwards.
These gases in turn exert a reaction force on the balloon and make it move forward.
That is, opposite to the direction of the ejected gas.
Experimental materials and tools
A balloon.
(2) a short rope used to tie the balloon mouth.
(3) Use a long rope as the track for the balloon to slide.
(4) The drinking straw is sleeved on the long rope and slides with the balloon.
(5) Fix both ends of the long rope with two high-back stools.
(6) scissors and tape.
experimental procedure
The first step is to tie one end of a long rope to a bench with a high back.
Step two, put the straw outside the rope and be patient.
Insert it at one end of the straw, insert it, and take the other end out.
Step three, blow up the balloon. Look at me. My vital capacity is dripping.
Take a deep breath, then blow hard and stick to it.
Step four, tie the mouth of the balloon with a short rope.
Note that you should tie a slipknot so that you can untie it later.
Step 5, fix the balloon under the straw with adhesive tape and stick it firmly.
In this way, the balloon and the straw are integrated and can slide on the long rope.
Step six, untie the short rope that binds the balloon mouth.
Only heard a "poof-poof" sound, and the balloon ejected a stream of gas backwards.
Under the action of this airflow, the balloon glides along the rope with a straw.
In an instant, the balloon was completely deflated and the stomach was deflated.
At the same time, the balloon also slid along the rope for a distance of about one meter.
Haha, my rocket launch was a complete success.