A sample of 80 g of a radioactive isotope has a half-life of 3 days. How much remains after 12 days?
Answer and explanation
Correct answer: C. 5 g
- Step 1: 12 days is half-lives. Step 2. g. Answer: 5 g. Why not the others: 10 g and 20 g use three or two half-lives; 26.7 g divides by 3 once.
Practise more Electricity, Magnetism, Optics and Modern Physics.
Free questions with an explanation for every one, and full timed Wazari Exam (Iraq Baccalaureate) - Scientific Branch mock tests.
More Electricity, Magnetism, Optics and Modern Physics questions
- A 12 V battery is connected across a 4 ohm resistor. What current flows?
- A 6 ohm and a 3 ohm resistor are connected in parallel. What is their combined resistance?
- A current of 2 A flows through a 5 ohm resistor. What power is dissipated?
- A 10 microfarad capacitor is charged to 100 V. How much energy does it store?
- Point charges of 2 microcoulomb and 3 microcoulomb are 0.3 m apart in air. What is the magnitude of the force between them? (…
- A straight wire 0.2 m long carries 4 A at right angles to a uniform field of 0.5 T. What is the force on the wire?