Answer:
U-238
Explanation:
For a given radioisotope, half life can be defined as the time taken for the isotope to decay into one-half of its original amount. Mathematically, this is expressed as:

where k = rate constant for the radioactive decay process
Greater the t1/2 longer will be its stability.
Based on the given data, U-238 has the largest half life and therefore will be best suited for applications mentioned.
The purpose<span> of preparing </span>Set-up<span> _ is to act as a </span>control set-up<span> to ensure that the (measured variable) is only caused by the(changed variable) and not any other variables in the experiment.</span>
Answer: 2m/s^2
Explanation:
Velocity of skateboard = 20.0 m/s.
Time taken = Ten seconds (10 s)
Acceleration = ?
Recall that acceleration is the change in velocity of a body per unit time.
i.e Acceleration = (velocity / Time)
Acceleration = 20.0m/s ➗ 10 s
Acceleration = 2m/s^2
Thus, Jeffrey acceleration was 2m/s^2
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