Answer: half life
Explanation: Radioactive decay follows first order kinetics and the time required for the decay of a radioactive material is calculated as follows:

t= time required
k= disintegration constant
x= amount of substance left after time t
a= initial amount of substance
when one half of the sample is decayed, one half of the sample remains and t can be represented as 
at
, 


10 x 70 = 100 x Part, or
700 = 100 x Part
Now, divide by 100 and get the answer:
Part = 700 / 100 = <span>7</span>
The difference between the wattage is 60-18=42W. The saving in energy over 10 hrs is 10×42=420 watt-hours=0.42kWh
The distinguishing characteristics of comets, meteors, and asteroids are its composition.
<h3>What are the characteristics of comets, meteors and asteroids?</h3>
Asteroids are the fragments of rock that were left over from the creation of the solar system, Meteors are the rocks that enter the atmosphere of the Earth from space while on the other hand, Comets are the remnants of the formation of the solar system that are made of dust, rocks, and ice. All these materials i.e. comets, meteors and asteroids are different from one another due to its structure and chemical composition.
So we can conclude that the distinguishing characteristics of comets, meteors, and asteroids are its composition.
Learn more about asteroids here: brainly.com/question/11996385
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