A sound wave is incident on a pool of fresh water (25 °C). The sound enters the water perpendicularly and travels a distance of 0.45 m before striking a 0.15-m-thick copper block lying on the bottom. The sound passes
through the block, reflects from the bottom surface of the block, and returns to the top of the water along the
same path. How much time elapses between when the sound enters and when it leaves the water?

Thomas his older brothers, who own a junk yard, on the weekends to earn extra money. he likes to them push broken-down cars to the back of the junk yard because it makes him feel strong. last saturday, they pushed three cars with different weights, and he noticed he used different amounts of force for each one. the cars were the following weights: white car: 2,700 kg red car: 1,500 kg blue car: 2,100 kg think about how much force is needed to move each car. which correctly lists the cars in order from the most to least amount of force needed to move them? a) white, blue, red b) blue, red, white c) red, white, blue d) white, red, blue

Gasoline comes from petroleum, which is made from ancient living things. petroleum, therefore, contains a type of energy. a. heat b. nuclear c. biological d. chemical potential

If we relied solely on the nonrenewable resources found in the u.s., which one would we run out of first at current usage levels? a. natural gas b. oil c. uranium d. coal