APHY 140 Practice Exam p2, p3
Light travels at approximately 3.0 × 10^m/s^2 , given that there are 1.61 km in a mile, how many
miles will light travel in one year? That is, how many miles are there in one Light-Year? - ✔✔ correct
answer 5.882×10^12 miles
The diameter of a human red blood cell is about 0.008 mm. Write this diameter in micrometers 𝜇𝑚 -
✔✔ correct answer 0.008 mm * 1000 μm/mm = 8 μm
The radius of the Earth is 6378 km. What is the circumference of the Earth in miles?
(1.61 km = 1 mi) - ✔✔ correct answer 24882.36 mi
In 1873, Jules Verne wrote the novel Around the World in Eighty Days. Given the circumference of
the Earth found in the previous problem, what would the average speed be (in mi/hr) of a person
going around the world in 80 days? - ✔✔ correct answer 12.99 miles per hour
A typical lecture is about 1 microCentury long. How many minutes is that? (A century is 100 years) -
✔✔ correct answer 1×(100×365.25×24×60) = 5,256,000
If one went around the world in 80 days, what would the average angular velocity be in rad/sec? -
✔✔ correct answer 9.08×10^−7 rad/s
A CD player is designed to read data from the CD at a constant linear rate of about 1.28 m/s . The CD
begins reading from the inner edge out to the outer edge of the disk at about 58 mm from the
center. What is the angular speed of the CD as it reads at the outer edge of the CD, at 12.4 cm from
the center? - ✔✔ correct answer 22.07 rad/s
An astronaut on the Moon, drops a feather from a height of 1.5m. Given that the acceleration of
gravity on the lunar surface is 1/6-th the acceleration of gravity on Earth's surface: 𝑔_moon = 1/6
𝑔_earth , how long does it take for the feather to fall and hit the ground? - ✔✔ correct answer 1.354
s
A car driving at 65 mph slams on its brakes. If the brakes decelerate the car at 𝑎 = −5 m/s^2, how far
will the car travel before it stops? - ✔✔ correct answer 84.17 meters
A guard, named Hodor, pushing hard on the large iron gate he is guarding can accelerate it with an
angular acceleration of 𝛼 = 0.03 rad/s^2. A troll is lumbering rather quickly toward the gate, and the