The arrows in models of magnetic and electric fields show both their magnitude and direction.
In Physics, a vector refers to a quantity that has both magnitude and direction. Hence, a vector always points in a given direction. The direction in which the arrow points is the direction of the vector in space.
In models of magnetic and electric fields, field vectors depicted by arrows because they represent both their magnitude and direction. The length of the arrow shows magnitude.
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Well we can't see the picture that the teacher has, and we have to figure out what's in the picture from some clues in the answer choices. The picture seems to show an atom with 3 protons and 3 neutrons in the nucleus, and 3 electrons whizzing around the nucleus.
If that's what's in the picture, then Mike is correct (first choice), because the atomic number shows the number of protons in all atoms. There are 3 protons and the atomic number of lithium is 3.
Second choice . . . False, because electrons are not involved in the atomic mass.
Third and fourth choices . . . both false; sadly, Joan is woefully unclear on the concepts.
Answer:
It will have an acceleration of .
Explanation:
Newton’s second law is defined as:
(1)
Equation 1 can be rewritten for the case of the acceleration:
The force and the acceleration are directly proportional (if one increase the other will increase too).
But 1 N is equivalent to
So a body will have an acceleration as a consequence of the action of a force.
How much gravitational potential energy does the block have
when it gets to the top of the ramp ?
(weight) x (height) = (15 N) x (0.2 m) = 3 Joules .
If there were no friction, you would only need to do 3 Joules of work
to lift the block from the bottom to the top.
But the question says you actually have to do 4 Joules of work
to get the job done.
Friction stole one of your Joules along the way.
Choice-4 is not the correct one.
Choice-1 is the correct one.
===========================
Notice that the mass of the block is NOT 15 kg , and you
don't have to worry about gravity to answer this question.
The formula for potential energy is (m)·(g)·(h) .
But (m·g) is just the WEIGHT, and the formula
is actually (weight)·(height).
The question GIVES us the weight of the block . . . 15 N .
So the potential energy at the top is just (15N)·(0.2m) = 3 Joules.