We want to get a better, more concrete idea of the strength of the electric force. So imagine you could remove all the electrons
from 1 mL (1 cubic centimeter) of water. Dump the electrons on yourself, and put the electron-free nuclei (protons and neutrons) on the moon. Estimate how much force will there be between the positive and negative charges? (Of course you have to look up the earth-moon distance.) What fraction of your weight is that force? How many electrons do you have in 1 cc? Consider that virtually all the mass is given by protons and neutrons. Since the proton and the neutron have almost equal masses, and most atoms have equal numbers of protons and neutrons, so the water mass, divided by 2, is the mass of protons. Once you know the total mass of protons, divide by the mass of a single proton and you have the total number of protons. Knowing that, how many electrons do you then suppose you have?)
2 answers:
Answer:
The electric force is 2.2962c + 005 times the gravity force on average human.
Explanation:
Get mass of water in gm
get the mass of protons in 1mL water
get number of electrons that should be present in 1mL of water
electric force Np (protons number), Ne (electrons number)
then get the ratio between the Electric force and weight of average human body;
see workings in attached picture.
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a) 0 kg m/s
b) 0 kg m/s
c) +3 m/s
d) 60 N
Explanation:
a)
The momentum of an object is a vector quantity given by:
where
m is the mass of the object
v is the velocity of the object
In this problem, we have a system of two people, so the total momentum will be the sum of the individual momenta of the two people:
Which can be rewritten as
where are the masses of the two people and
their initial velocities.
However, the two people are initially at rest, so
Therefore the total momentum is
b)
The principle of conservation of momentum states that when there are no external forces acting on a system, the total momentum of the system is conserved, so we can write:
where
is the total momentum of the system before
is the total momentum of the system after
In this problem,
As we calculated in part a: this is because the total momentum of the two people before they push off each other is zero.
Therefore, according to the law of conservation of momentum,
So the total momentum is zero also after they push off each other.
c)
The total momentum of the girl and the boy after they push off each other can be written as:
(1)
where:
is the mass of the girl
is her velocity (she moves backward, so the negative sign)
is the mass of the boy
is the velocity of the boy
As calculated in part b), we also know that the total momentum of the girl and the boy is
(2)
By combining eq(1) and eq(2) we get
And solving for v2 we find the velocity of the boy:
and the positive sign means he is moving forward.
d)
We can solve this part by applying the impulse theorem, which states that the change in momentum of an object is equal to the product between the force applied on it and the duration of the collision:
where
is the change in momentum
F is the force
is the time during which the force is applied
In this problem:
For the boy, the change in momentum is:
And since
We have
So, the force exerted between the boy and the girl is:
Answer: 3.63 km/s
Explanation:
The escape velocity equation for a craft launched from the Earth surface is:
Where:
is the escape velocity
is the Universal Gravitational constant
is the mass of the Earth
is the Earth's radius
However, in this situation the craft would be launched at a height over the Eart's surface with a space elevator. Hence, we have to add this height to the equation:
Finally:
Answer:
the radii of curvature is 30 cm.
Explanation:
given,
object is place at = 45 cm
image appears at = 90 cm
focal length = ?
refractive index = 1.5
radii of curvature = ?
f = 30 cm
using lens formula
R = 30 cm
hence, the radii of curvature is 30 cm.