20. A horizontal spring has a spring constant k = 345 (N/m). We compress it from its uncompressed length x = 0 to x = −13 (cm). A block with 3.32 (kg) is placed against the spring, and the spring is released. Find the speed of the block when the block returns to its uncompressed length. (A) 2.76 m/s (B) 4.53 m/s (C) 5.64 m/s (D) 1.33 m/s

10. The number of collisions a molecule makes per second is called collision frequency. At one atmosphere and 0 °C, estimate the collision frequency of air molecules. [The diameter of an air molecule under one atmosphere and 0 °C is approximately 3×10⁻¹⁰ (m), the average molecular speed is approximately 460 (m/s), and the molecular number density is approximately 2.7×10²⁵ molecules/m³]. (A) 3.5×10⁵ (collisions/s) (B) 3.5×10⁷ (collisions/s) (C) 3.5×10⁹ (collisions/s) (D) 3.5×10¹¹ (collisions/s)

相關試題

相關試卷