A 50 kg student holding a 7 kg backpack rides a 4 kg skateboard down the sidewalk at 3 m/s. What is the total momentum of the student, backpack, and skateboard?

Ahypothetical metal has an orthorhombic unit cell for which the a, b, and c lattice parameters are 0.413 nm, 0.665 nm, and 0.876 nm, respectively. (a) if there are 8 atoms per unit cell and the atomic packing factor is 0.536, determine the atomic radius (in nm). (b) if the density is 3.99 g/cm3, calculate the metal's atomic weight (in g/mol).