Explain what is observed when the temperature of water, which has pollen grains suspended in it, is raised.
(2 marks​

The phenomenon of the irregular movement of pollen grains suspended in water was observed by Robert Brown in 1827. Brownian motion, the name given to this process, was not given a rigorous mathematical treatment until almost one hundred years later by N.

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.