There is a cylindrical shape sweet potato with an initial uniform temperature of 25°C and it has an average diameter of 70 mm and length of 150 mm. Thermal conductivity and diffusivity of the sweet potato are 0.62 W/m · °C and 0.2 x 10-6 m2/s, respectively. It is to be cooled by refrigerated air at 1.8°C. The average heat transfer coefficient between the potato and the air is 25 W/m2 · °C. Determine how long it will take for the center temperature of the potato to drop to 5.5°C.

Explanation:

The given data is as follows.

    ,    d = 70 mm =

    k = 0.62 ,    

    ,    v = 4 m/sec

       h = 25 ,  

First, we will calculate the value of as follows.

                    =

                    = 0.7056

Since, 0.7056 is greater than 0.1.

As,   = 0.159

                = 0.16

Also here,

              = 1.9

            = 1.9

                 T = 46.18 hrs

Thus, we can conclude that it will take 46.18 hrs for the center temperature of the potato to drop to .

the box does not move because you need to use a force greater than 300 n. you are only using 50 n. it needs to at least be 301 n for the box to move because then it is an unbalanced force and it will move the way that the greater force is pushing it. if you use only 300 n it will be a balanced force and will not move because the force you are exerting on the   box is the same as its force.

hope this !

im sorry if i went too in depth, i am going to include a link to a video on khan academy that will explain this.   hope that you like the video and that it explains more in detail to you.

that is the link.