An attractive force of 7.2 N occurs between two point charges that are 0.10 m apart. If one charge is 4.0 µC, what is the other charge? (µC = 1.0 × 106 C)
(Points : 3)
1.0 µC
2.0 µC
+1.0 µC
+2.0 µC
Which substance is most easily grounded?
(Points : 3)
plastic foam plate
copper rod
rubber tire
PVC pipe
F=kq₁q₂/r²
q₂= F r²/kq₁= 7.2•10⁻²/9•10⁹•4•10⁻⁶=
=2•10⁻⁶ C = 2μC
Cpper rod is an electrical conductor; the others are insulators.
To find the charge of the other point, we can use Coulomb's law. According to Coulomb's law, the force between two point charges is given by the equation:
F = k * (q1 * q2) / r^2
where F is the force between the charges, k is the electrostatic constant (9 × 10^9 N m^2/C^2), q1 and q2 are the magnitudes of the charges, and r is the distance between the charges.
In this case, F = 7.2 N, q1 = 4.0 µC = 4.0 × 10^-6 C, and r = 0.10 m. Let's solve for q2:
7.2 = (9 × 10^9) * (4.0 × 10^-6) * q2 / (0.10)^2
Multiplying both sides by (0.10)^2 and dividing both sides by (9 × 10^9) * (4.0 × 10^-6), we get:
q2 = 7.2 * (0.10)^2 / ((9 × 10^9) * (4.0 × 10^-6))
Calculating this, we find:
q2 ≈ 0.080 µC
Therefore, the charge of the other point is approximately 0.080 µC.
To calculate the value of the other charge, we can use Coulomb's law, which states that the force between two point charges is proportional to the product of their charges and inversely proportional to the square of the distance between them.
The formula for Coulomb's law is:
F = k * |q1 * q2| / r^2
Where:
F is the attractive force between the charges,
k is the electrostatic constant (9 * 10^9 N m^2/C^2),
q1 and q2 are the charges, and
r is the distance between the charges.
In this case, we are given that the attractive force is 7.2 N, the distance between the charges is 0.10 m, and one of the charges is 4.0 µC.
We can rearrange the formula to solve for the other charge (q2):
q2 = F * r^2 / (k * |q1|)
First, let's convert the charge q1 from microcoulombs (µC) to coulombs (C):
4.0 µC = 4.0 * 10^-6 C
Now, we can substitute the given values into the equation:
q2 = 7.2 N * (0.10 m)^2 / (9 * 10^9 N m^2/C^2 * |4.0 * 10^-6 C|)
Simplifying the equation:
q2 = (7.2 * 0.01) / (9 * 10^9 * 4.0 * 10^-6)
q2 = 0.072 / (36 * 10^-3)
q2 = 0.072 / 3.6 * 10^-2
q2 = 0.072 / 3.6 * 10^-2
q2 = 2 * 10^-2 C
Therefore, the value of the other charge (q2) is 2.0 µC.
So, the correct answer is option 2: 2.0 µC.
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To determine which substance is most easily grounded, we need to understand that grounding is a process of removing excess electric charge from an object by allowing it to flow into the Earth through a conductive pathway.
The substance that is most easily grounded is the one that is the best conductor of electricity. This means that it has free-moving charges (typically electrons) that can easily flow through it.
Copper is a highly conductive material and is commonly used as a conductor in electrical systems. It allows electric charges to flow easily, making it an excellent choice for grounding.
For this reason, the correct answer is option 2: copper rod.