Q1. A student drops a penny from the top of a tower and decides that he will establish a coordinate system in which the direction of penny's motion is positive. What is the sign of the acceleration of penny?
Q2. A 40.0 cm diameter cylinder of helium gas is 70.0 cm long and at 30.0 ^circC. The pressure gauge reads 140 psi. How many helium atoms are in the cylinder?