Time flies, this semester is coming to an end. We have learned Unit 7. The last unit is math fun. Teacher Yang asked us to do experiments. Gave us time to discuss. Our decision is as follows:

? I brought basketball, Cui Yuze brought table tennis, Zhao brought notebook records and He Ziqian brought a tape measure.

In this way, we assigned the work. Everyone has his own belt. During the break on Thursday, we conducted an experiment. I'll press the steel tape against the wall first and straighten it as straight as possible, otherwise the accuracy of the experiment will be different.

? The purpose of our experiment is, at the same height, what is the rebound height of basketball and table tennis without exertion? Who plays high?

? We use a skipping rope to aim at the steel tape 130cm. I saw Cui Yuze's basketball fall with a bang. Our eyes are fixed on the steel tape measure. This is the data of five experiments.

The height of the first rebound in basketball is 99cm.

The height of the second basketball rebound is 95cm.

The height of the third basketball rebound is 97cm.

The height of the fourth backboard in basketball is 96cm.

The height of the fifth backboard in basketball is 97cm.

The experiment of basketball is finished, and then we start the experiment of table tennis.

The height of the first backboard of table tennis is 23cm.

The second jumping height of table tennis is 15cm.

The height of the third backboard of table tennis is 26cm.

The height of the fourth backboard of table tennis is 25cm.

The fifth rebound height of table tennis is 23cm.

? The experiment is over, and we have come to a conclusion, that is. The rebound height of basketball is related to the ground, because we conducted the experiment on the artificial lawn. The place where people often step on will be more solid, the rebound height of basketball will be higher, the place where no one often steps on will be looser, and the rebound of basketball will be shorter. This will affect the experimental data.

? Another factor is whether the motivation of basketball is sufficient and full. A ball with more gas will bounce high, and a ball with less gas will bounce short or even fail to bounce.

? There should be another factor: the materials of basketball and table tennis are different. The skin of basketball is soft, but the skin of table tennis is hard. So the experimental results are different.

? It can be confirmed that height and strength have nothing to do with the result, because our height is 130cm, and there is no strength. So there can't be this factor.

? The average rebound height of basketball is 96.8cm, and that of table tennis is 23.2cm, which shows that the average rebound height of basketball is higher than that of table tennis.

? Of course, in order to calculate accurately. We decided to round off, round off 96.8cm to 97cm and 23.2cm to 23cm. This is easier to calculate.

? The rebound height of basketball is about a fraction of the starting height. We can use 97 ÷ 130 = 130/97, and the rebound height of table tennis can also be calculated by this method. 23÷ 130= 130/23。

? After this experiment, I know that the experiment can't be successful once, and such data is inaccurate. It is best to experiment many times. The more experiments, the higher the accuracy.