Truyền động trên nguyên lý Ma sát, ăn khớp hoặc kết hợp ma sát + ăn khớp ?

Explain the difference laminar and turbulent flow. explain it with the shear stress and the velocity profiles.

Modern high speed trains do not have perpendicular expansion gaps where rails are joined end-to-end any more they are mostly welded together but what might happen if there was a spell of particularly hot weather that causes inspection of the tracks?

For a gate width of 2 m into the paper, determine the force required to hold the gate abc at its location.