Answer:
E_total = 1.30 10¹⁰ C / m²
Explanation:
The intensity of the electric field is
E = k q / r²
on a positive charge proof
The total electric field at the midpoint is
as q₁= 6 10⁻⁶ C the field is outgoing to the right
for charge q₂ = -3 10⁻⁶ C, the field is directed to the right, therefore
E_total = E₁ + E₂
E_total = k q₁ / r₁² + k q₂ / r₂²
r₁ = r₂ = r = 4 10⁻² m
E_total = k/r² (q₁ + q₂)
we calculate
E_total = 9 10⁹ / (4 10⁻²)² (6.0 10⁻⁶ +3.0 10⁻⁶)
E_total = 1.30 10¹⁰ C / m²
The tension in the string B) It quadruples.
Explanation:
The ball is in uniform circular motion in a horizontal circle, so the tension in the string is providing the centripetal force that keeps the ball in circular motion. So we can write:

where:
T is the tension in the string
m is the mass of the ball
v is the speed of the ball
r is the radius of the circle (the lenght of the string)
In this problem, we are told that the speed of the ball is doubled, so
v' = 2v
Substituting into the previous equation, we find the new tension in the string:

Therefore, the tension in the string will quadruple.
Learn more about circular motion:
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The answer is
Pitch of the buzzer increased (higher tone) as it moves towards the observer
B. only its velocity should change
Answer:
<em>The kinetic energy of a spinning disk will be reduced to a tenth of its initial kinetic energy if its moment of inertia is made five times larger, but its angular speed is made five times smaller.</em>
<em></em>
Explanation:
Let us first consider the initial characteristics of the angular motion of the disk
moment of inertia = 
angular speed = ω
For the second case, we consider the characteristics to now be
moment of inertia =
(five times larger)
angular speed = ω/5 (five times smaller)
Recall that the kinetic energy of a spinning body is given as

therefore,
for the first case, the K.E. is given as

and for the second case, the K.E. is given as


<em>this is one-tenth the kinetic energy before its spinning characteristics were changed.</em>
<em>This implies that the kinetic energy of the spinning disk will be reduced to a tenth of its initial kinetic energy if its moment of inertia is made five times larger, but its angular speed is made five times smaller.</em>