I can't guess what -9.8 m/s means until you tell me where it came from,
or what 'm/s' means.
If perhaps it has something to do with the acceleration of gravity on Earth,
then the correct figure is ' -9.8 m/s² '. That means that any object that
has no other force acting on it except gravity has its speed changing by
9.8 meters per second every second. Since it's gravity doing the job,
then the object's speed is either increasing down, or decreasing up.
If an object has negative velocity, then it's moving in the direction opposite
to the direction that you decided to call positive when you started doing the
problem.
For example, if you decide that up is positive and down is negative, and
then somebody drops a stone from the top of a tall building, then the
gravitational force on the stone is negative (pointing down), its velocity
is negative (it's falling towards down), and its acceleration is negative (its
speed towards down is getting faster and faster). Everything is negative,
only because you decided that up is positive and down is negative. It's
nothing to be worried about.
I couldnt type it out so here's a picture
Answer: Dalton’s model
Explanation:
In the attached image we can see four atomic models labeled with four letters:
W represents the current and accepeted atomic model: a nucleus with an electron cloud, where the orbit and position of the electrons around the nucleus is defined by specific regions (associated with specific energy levels) where there is a greater probability of finding the electron at any given moment. It is important to note this model was improved by the works in quantum physics done by Louis de Broglie and Erwin Schrodinger.
X represents Rutherford's model (This model was proposed after Thomson's model). Ernest Rutherford conducted a series of experiments in order to corroborate Thomson's atomic model. However the results of the experiment led him to find out there is a concentration of charge in the atom's core (which was later called nucleus) surrounded by electrons. This lead to a new atomic model, in which the atom has a positive charged nucleus surrounded by negative charged particles that move similar to the orbit of the planet around the Sun.
Y represents Thomson's model, also called the <em>plum pudding</em> model. This scientific found out that atoms contain small subatomic particles with a negative charge (later called electrons). However, taking into consideration that at that time there was still no evidence of the atom nucleus, Thomson thought the electrons were immersed in the atom of positive charge that counteracted the negative charge of the electrons. Just like the raisins embedded in a pudding or bread.
Z represents Bohr's model. This model was proposed by the danish physicist Niels Bohr after Rutherford's model. In fact, this model was Rutherford's model with the following addition: electrons orbit the nucleus (like planets around the sun) in specific orbits at different energy levels around the nucleus.
So, the only missing model is <u>Dalton's model</u>, which was the first atomic model: the atom represented as a solid, indestructible and indivisible mass. An idea that was already accepted by that time since the ancient Greeks.
Answer: 
Explanation:
We can solve this problem using the <u>Poiseuille equation</u>:
Where:
is the Volume flow rate
is the effective radius
is the length
is the difference in pressure
is the viscosity of blood
Solving: