Do changes in scientific knowledge occur often?

Waves that cause the most damage during an earthquake are a. surface waves c. s waves b. p waves d. ocean waves

You are driving directly behind a pickup truck, going at the same speed as the truck. a crate falls from the bed of the truck to the road. (a) will your car hit the crate before the crate hits the road if you neither brake nor swerve? (b) during the fall, is the horizontal speed of the crate more than, less than, or the same as that of the truck?

Glass has a hardness that is in the middle of the hardness scale. what is the hardness of glass?