Return to MCAT® Blog
Homepage
MCAT Physics Question — Half Life
- by
- Mar 20, 2017
- MCAT Question of the Day
- Reviewed By: Liz Flagge
If the half-life of carbon-14 is 5700 years, and some plant remains from an archeological dig site have 1/8 the carbon-14 found in the atmosphere, what is the approximate age of the remains in the dig site in years?
- 700
- 5700
- 17000
- 45000
Click for Explanation
The half-life is the time it takes for 1/2 of a radioactive substance to decay. For example, 20 units of a substance with a half-life of 5 years will have 10 units remaining after 5 years. In this example, carbon-14 has undergone 3 half-lives: 1 → ½; ½ → ¼; ¼ → 1/8.
3 x 5700 years = 17100 years.
- 700, incorrect, This answer results from multiplying the amount of sample by the half life, 5700/8.
- 5700, incorrect, This is the half-life, not the amount of time elapsed during three half-lives.
- 17000, correct.
- 45000, incorrect, This answer results from multiplying the half-life by the remaining fraction: 5700 x 8.
Want more MCAT practice?
We’ve got options for every schedule and learning style!
From the best online MCAT course created by top instructors with 524+ MCAT scores to the most representative full-length practice exams and private tutoring, we can custom tailor your MCAT prep to your goals!
Not sure which option is right for you? Schedule a free MCAT consultation with an MCAT expert using the form below. No obligation, just expert advice.
Related Posts
Search the Blog
Free Consultation
Interested in our Online MCAT Course, One-on-One MCAT Tutoring or Med admissions packages? Set up a free consultation with one of our experienced Senior Student Advisors.
Schedule NowPopular Posts
-
-
MCAT Blog What's on the MCAT? -
-
-
MCAT Blog How to Review MCAT Full Lengths
Free MCAT Practice Account
Need great MCAT practice?Get the most representative MCAT practice possible when you sign up for our free MCAT Account, which includes a half-length diagnostic exam and one of our full-length MCAT practice exams.
Learn More