Obtain an expression for minimum velocity at the highest point in the motion of the particle in vertical circulation

1/0.14nm = 10^10/1.4 a lot

this is poiselle's equation from fluid mechanic in physics. mech eng

a.) travels faster in solids because the particles are closer together.

air is a gas water is a liquid

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.