What tool is this and what is this tool used for

Apreheater involves the use of condensing steam at 100°c on the inside of a bank of tubes to heat air that enters at 1 atm and 25°c. the air moves at 5 m/s in cross flow over the tubes. each tube is 1 m long and has an outside diameter of 10 mm. what is the minimum value of nl needed to achieve an outlet temperature of t 75 c? what is the corresponding pressure drop across the tube bank?

Aparticle moves along a straight line such that its acceleration is a=(4t^2-2) m/s, where t is in seconds. when t = 0, the particle is located 2 m to the left of the origin, and when t = 2, it is 20 m to the left of the origin. determine the position of the particle when t=4s.

Aflow moves in the x direction with a velocity of 10 m/s from 0 to 0.1 second and then reverses direction with the same speed from 0.1 to 0.2 second. sketch the pathline strating from x-0 and the streak! ine with dye introduced at x=0. show the streamlines for the first time interval and the second time interval.