## 2.1 Apparatus

17 people, stop watch, playground.

## 2.2 Procedures

- Everyone put their hands on carotid artery.
- Timekeeper calculate the time use.
- Once the timekeeper call "start!", students can begin to count the heartbeat.
- Repeat 3 times and get 3 different groups of data.
- All the students run 5 minutes continuously.
- Repeat the procedure 1-3 every half a minutes for 7 times.

## 2.3 Data

To get a obvious and simple curve, for each item, I just calculate the average value.

## 2.4 Observations

The intensity of the excise may be different from each one. Because some people ran fast, some people ran slowly.

## 3.0 Analysis

## 3.1 Experimental value

From the graph, we can get the equation, 155.89 can be rounded to 156 which is the original number of heartbeat after excising. -0.0934 is the decay constant which represent .

## 3.2 Data Analysis

This is the heart rate that our body will decrease to after an exercise session. After exercise in a 1/2 hour at 155. Two minutes our heart rate decreases to 85. The 85 would be our recovery heart rate. It's the straight line labeled on the graph.

## 4.0 Discussion

## 4.1 Error Analysis

### 4.1.1 Gross Error

- When the timekeeper recording the time, the stopwatch may cut-out because of the rainwater, the data which is being record may got lost.
- After running, the situation may be complex, the timekeeper can not hear the runner clearly when they told the number of heartbeat, the timekeeper may got the wrong data.

### 4.1.2 Systematic Error

- Different people have different physique, 5-minute running may be a big challenge to most of the students, their bodys or hearts can generate different reaction after excising, the number of heartbeat can also be various.
- The distance which students ran through can be different as well, so students' number of heartbeat can be different.

### 4.1.3 Random Error

- In the running process, because of the rainwater on the playground, someone fell down, the blood pressure got high, the heartbeat increased.
- After running, the excising can result of lack of oxygen to the brain. Students can not remember how many the heartbeat was they just count.

## 4.2 Why the line can not approach the asymptote?

Theoretically, the curve can approach to the straight line above infinitely, but we can't see on the graph, it may caused by insufficient data after running.

## 5.0 Conclusion

Form the experiment, by measuring students' number of heartbeat after running , we got the curve Heartbeat v.s Time and got the decay constant from excel. The decay constant of this decay is -0.0934.