Hi there!
We can use Newton's Second Law:

∑F = net force (N)
m = mass (kg)
a = acceleration (m/s²)
We are given the mass and acceleration, so:
∑F = 20 · 2 = <u>40 N</u>
Answer:
B) Within an atom, an electron can have only particular energies.
Explanation:
As we know that electrons have energy but apart from electrons we know that protons and neutrons inside the nucleus of atom will also have energy in them.
rest all the statements are true as we have
A) Electrons orbit the nucleus rather like planets orbiting the Sun.
TRUE, because electrons can move in stationary orbit around the nucleus
C) Electrons can jump between energy levels in an atom only if they receive or give up an amount of energy equal to the difference in energy between the energy levels.
Difference amount of energy is lost or absorbed by the electron in form of photons
D) An electron has a negative electrical charge.
Charge of an electron is given as 
E) Electrons have very little mass compared to protons or neutrons
Mass of an electron is given as

mass of proton or neutron

Answer:
The slope of a position-time graph can be calculated as:

where
is the increment in the y-variable
is the increment in the x-variable
We can verify that the slope of this graph is actually equal to the velocity. In fact:
corresponds to the change in position, so it is the displacement, 
corresponds to the change in time
, so the time interval
Therefore the slope of the graph is equal to

which corresponds to the definition of velocity.
Answer:
It is green. Aside from being renewable, tidal energy is also an environmentally friendly energy source because it does not take up a lot of space and does not emit any greenhouse gases.
Explanation:
Answer:
ratio =0.3075 T
Explanation:
The magnetic field B creates a force on a moving charge such that

Now this causes a centripetal acceleration

so
...........(i)
...............(ii)
If accelerating potential V is same and then kinetic energy equals the potential energy difference

put these value in equation (ii)
simplifying we get

for same location r will be same in both case
..............(iii)
..........(iv)
dividing (iv) and (iii) equation we get



so on solving we get
=0.3075 T