问题
填空题
放射性元素A的半衰期为3天，B的半衰期为6天，有16克A元素和4克B元素，问B经过 个半衰期才能使它们的质量相等，这时质量为 。
答案
2、1克
题目分析：根据半衰期的定义可得
，代入数据解得t=12天，所以B经过2个半衰期才能使它们的质量相等，此时
。
点评：半衰期公式为
，其中
为衰变前的质量，m为衰变后的质量，T为半衰期，t为衰变时间。
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放射性元素A的半衰期为3天，B的半衰期为6天，有16克A元素和4克B元素，问B经过 个半衰期才能使它们的质量相等，这时质量为 。
2、1克
题目分析：根据半衰期的定义可得，代入数据解得t=12天，所以B经过2个半衰期才能使它们的质量相等，此时。
点评：半衰期公式为，其中为衰变前的质量，m为衰变后的质量，T为半衰期，t为衰变时间。
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