# Recitation 1R

1. How large would a critical mass of pure Uranium-235 be?
2. How many suitcases does it take to carry \$1 billion worth of gold?

Now let's do some more quantitative calculations, in which we keep track of the uncertainties and express the results with the proper number of significant figures.

1. Until 1997, university education in the United Kingdom was free; that is, the students were not required to pay any tuition. Taxpayers funded the entire university system.

Suppose that the US decided to follow this policy. Estimate the annual cost of educating all university students in the US. Include an uncertainty.

How large is this number compared to the entire budget of the US Department of Education?

How large is this number compared to the entire budget of the US government?

2. I will toss a ball across this lecture hall. We will measure the distance the ball travels (with an uncertainty), and the time it takes the ball to make the trip (with an uncertainty). What is the velocity of the ball? Include an uncertainty.
3. One of the students in the class will come to the front of the room and jump upwards from a standing start. We will measure the time he remains in the air (with an uncertainty). Using a little kinematics, we'll determine how high his center of mass must have moved upwards, with an uncertainty.

Yes, we'll start kinematics soon. A little peek into the future won't hurt you.