Thallium has two isotopes thallium-203 and thallium-205 find which isotope is more abundant\abundance

Let we have X of Tl-205 so the percent of Tl-203 will be 100-X

Average mass of  Thallium is 204.4

Mass of  Tl-205=  

Mass of  Tl-203=  

So,

205X +20300-203X=20440

X=70

So the percent or abundance of  Tl-205 is 70 while that of Tl-203 will be 30.

for step 7 table c on the lab "newtons law of action"   the average time it took the car to travel .25 meters   was 1.92 seconds.

the average time it took the car to travel 0.50 meters was 2.61 seconds

hope this : )

i do not get it   at all