Question

A piston–cylinder device initially contains 70 L of liquid water at 25 °C and 300 kPa. Heat is transferred to the water at constant pressure until the entire liquid is vaporized.
Calculate the work.

Answer 1

Answer:

Let the initial velocity of the body be u m/s; and the constsnt acceleration be a m/s². Then displacemet (distance covered) of the body after t second is given by

s = u t + ½ a t²

The body covers 20 m in 2s and 80 m in 4 s.

20 = u×2 + ½ a 2²; => 20 = 2 u + 2 a

u + a = 10

80 = u×4 + ½ a 4²; => 80 = 4 u + 8 a; this gives,

u + 2 a 38

Solving (2) and (3) for u and a we get

u = 0 m/s and a = 10 m/s²

To obtain the distance covered in the next 4s we need to find the velocity at the beginning of this interval using,

v = u + a t => v = 0 m/s + 1...