Suppose a small metal object, initially at a temperature of 50 degrees, is immersed in a room which is held at the constant temperature of 90 degrees. It takes 1 minutes for the temperature of the object to reach 70 degrees. Calculate the heat transfer coefficient r , i. e. the constant of proportionality in the differential equation that describes Newton's law of cooling.

An alpha particle with kinetic energy 12.5 mev makes a collision with lead nucleus, but it is not "aimed" at the center of the lead nucleus, and has an initial nonzero angular momentum (with respect to the stationary lead nucleus) of magnitude l = p0 b, where p0 is the magnitude of the initial momentum of the alpha particle and b=1.40×10−12 m. (assume that the lead nucleus remains stationary and that it may be treated as a point charge. the atomic number of lead is 82. the alpha particle is a helium nucleus, with atomic number 2.) what is the distance of closest approach?