There are several hypotheses as to why Earth's climate changed: an ice age and a meteor collision are two. Regardless of why the climate changed, dinosaurs could not adapt to a new environment to avoid extinction. Mammals did not become a dominant species on Earth until the extinction of dinosaurs
The acceleration would actually be 1.6 m/s^2. Acceleration= final velocity-initial velocity/time taken. When you do that formula it comes out to equal that.
