The half-life of uranium-235 is 713 million years. suppose a rock originally had 26 grams of uranium-235. a geologist had the rock tested, and found that it now has only 3.25 grams of uranium-235.

approximately how old is the rock?

2139 Million years

Explanation:

Half life of a material is the time required for the material to decay into half of initial amount.

initially there is 26 grams of uranium-235, and the final amount is 3.25 gram

                 ratio between initial and final amount =

now it is clear that the material have halved 3 times from initial condition

number of half lives passed = 3

number of half lives passed can also be found using the equation

                no of half lives =

where is the initial amount of material and R is the final amount

∵ Number of half lives =

                                      = 3

So, age of rock = half-life X number of half-lives passed

                          =713000000 X 3

                          = 2139000000

                          =2139 Million Years

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I'm having some difficulty seeing the diagram clearly.but the question says there's a net inward force on the object.so we know right away,  from newton's 2nd law of motion, thatthat baby is accelerating.  it doesn't even matter which way thenet force is pointing.  if there's any net force, then either theobject's speed or else its direction must be changing.