Why does the gravitational force between earth and moon predominate over electrical forces?
1 answer:
Answer:
Because the Earth and the Moon are electrically neutral
Explanation:
The gravitational force between the Earth and the Moon is given by
where G is the gravitational constant, m is the mass of the Moon, M is the mass of the Earth, r is the distance between the Moon and the Earth. Since both the Earth and the Moon have large masses, m and M are big, so the gravitational force between the two objects is large.
On the contrary, the electrostatic force between the Earth and the Moon is given by
where k is the Coulomb's constant, q1 is the charge of the Moon, q2 is the charge of the Earth, r is the distance between the Moon and the Earth. However, big objects (and planets as well) are electrically neutral, which means that they have zero charge (because if they had charge, they would tend to attract charge of the opposite sign, becoming neutral again). Therefore, the values of q1 and q2 are approximately zero, so the electrostatic force is zero as well.
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Answer:
A) 37 m
Explanation:
The car is moving of uniformly accelerated motion, so the distance it covers can be calculated by using the following SUVAT equation:
(1)
where
v = 0 m/s is the final velocity of the car
u = 24 m/s is the initial velocity
a is the acceleration
d is the length of the skid
We need to find the acceleration first. We know that the force responsible for the (de)celeration is the force of friction, so:
where
m = 1000 kg is the mass of the car
is the coefficient of friction
a is the deceleration of the car
g = 9.8 m/s^2 is the acceleration due to gravity
The negative sign is due to the fact that the force of friction is against the motion of the car, so the sign of the acceleration will be negative because the car is slowing down. From this equation, we find:
And we can substitute it into eq.(1) to find d: