Why have there been so many change to the atomic model? Under what circumstances should the atomic model be changed again?

Apendulum has a mass of 1.5 kg and starts at a height of 0.4 m. if it is released from rest, how fast is it going when it reaches the lowest point of its path? acceleration due to gravity is g = 9.8 m/s2. a. 2.8 m/s b. 0 m/s c. 5.9 m/s d. 4.3 m/s

Aknife blade is a(n) a. lever b. screw c. wedge d. inclined plane

An object moves from the position +34m to the position -15m in 15 seconds. what is it's total displacement? what is it's average velocity?