Physics School Exam Preparation

The background count rate measured by a radiation counter is 50 counts per minute (cpm). With the counter close to a radioactive source, the counter reading is 290 cpm. The half-life of the source is 15 minutes.

What is the counter reading one hour later?

• 65 cpm

• 15 cpm

• 18.125 cpm

• 68.125 cpm

The background count rate measured by a radiation counter is 10 counts per minute (cpm). With the counter close to a radioactive source, the counter reading is 26 cpm. The half-life of the source is 3 minutes.

What is the counter reading 9 minutes later?

• 2 cpm

• 12 cpm

• 13 cpm

• 3.25 cpm

What is the reading of GM counter after a half life of Uranium?

• 210 cpm

• 238 cpm

• 420 cpm

• 224 cpm

What is the reading of GM counter after a half life of Uranium?

• 210 cpm

• 240 cpm

• 420 cpm

• 225 cpm

1. What is the half-life of this isotope?

• 400 minutes

• 2 days

• 2 minutes

• 400 days

1. What is the half-life of this isotope?

• 10 years

• 13.5 years

• 600 years

• 21 years

1. What is the half-life of this isotope?

• 2 days

• 1 days

• 1250 days

• 1000 days

1. What is the half-life of this isotope?

• 20 days

• 15 days

• 20 hours

• 15 hours

1. What is the half-life of this isotope?

• 2 days

• 1 day

• 2 hours

• 1 hour

The orbit of the Moon around the Earth can be thought of as following a circular path with a circumference of 2.4 × 10⁶ km and that the Moon's orbital period is 27.3 days. What is the approximate orbital speed of the Moon?

• 1.002 km/s

• 3.683 km/s

• 5.288 km/s

• 30 km/s