Air is flowing steadily through a horizontal, constant diameter pipe. The pipe wall is heated uniformly so that the temperature of the air increases as the air flows through the pipe. You may assume that the air temperature is constant across the cross-section at any length down the pipe. If the air pressure remains constant (pressure drop is small enough to ignore), what can you say about the average velocity of air in the pipe? velocity remains constant since flow is steady (b) velocity will increase because increased temperature indicates the air molecules are moving faster and have higher kinetic energy (c) velocity remains constant because pipe is rigid so air can't expand or change density