First you need to make a difference between friction while object is stationary and the friction while object is moving. Force required to start moving some object is slightly greater than force required to maintain objects movement. That means that to move a chair you need some force F1 but you can than slightly reduce force and chair will still be moving.
Now to the problem in this question: It can be said that "stationary friction force" is equal to 15 Newtons. Its also good to know that friction force between chair and floor while you are increasing your push is also increasing and is equal to force of your push. Once it reaches 15N which is it "critical value" for that chair, chair starts moving and friction force drops a little bit and now it is called friction force of moving chair.
For the writer, scientific models are paradigms of set of patterns that is assumed to happen in a particular situation or circumstance which is why it was created and modeled, to explain a certain phenomenon. Take for instance the biogeochemical cycle model –water cycle. The water cycle model involves the different process which was observed happen as the current cycle has been experimented and predicted to happen again with the same process. <span>
</span>Models can represent things that are too small to see. <span> Scientists rely on models to represent concepts and processes in physical science because models can represent things that are too small to see. In fact, they are actually used to give a better perspective of what is occurring on these hidden to the naked eye matters –which may include atoms, cells, and entities unseen and latent. It gives scientists the ideas and structure, restructure, integrate and ponder on new hypothesis on these matters. <span> </span></span>
sorry, it's B, not a made a mistake in the approximation
~686newtons on earth and
~1617 newtons on jupiter
the formula is weight = gravitational acceleration * mass of the object
