A train car with a mass of 33,401 kg traveling north at 1.8 m/s collides and joins with a 39,190 kg train car going south at 0.7 m/s.  What is the velocity of the joined cars after the collision?

Which statement is true for light passing into a medium that is more optically dense than the first medium through which it past

Engineers find a new metal that is stronger than steel but much lighter. this material is also significantly cheaper than what is currently used for most aircraft, available in large quantities, and easy to manufacture. the engineers are excited because this new material will lower the costs of buying and operating airplanes for companies. what is probably the best step for the engineers to make next?

Matter is needed to transfer thermal energy bya. conductionb. convectionc. radiation d. both a & b.