Answer:
a) attractiva, b) dF =
, c) F =
, d) F = -1.09 N
Explanation:
a) q1 is negative and the charge of the bar is positive therefore the force is attractive
b) For this exercise we use Coulomb's law, where we assume a card dQ₂ at a distance x
dF =
where k is a constant, Q₁ the charge at the origin, x the distance
c) To find the total force we must integrate from the beginning of the bar at x = d to the end point of the bar x = d + L
∫ dF =
as they indicate that the load on the bar is uniformly distributed, we use the concept of linear density
λ = dQ₂ / dx
DQ₂ = λ dx
we substitute
F = 
F = k Q1 λ (
)
we evaluate the integral
F = k Q₁ λ
F = k Q₁ λ 
we change the linear density by its value
λ = Q2 / L
F =
d) we calculate the magnitude of F
F =9 10⁹ (-4.2 10⁻⁶)
F = -1.09 N
the sign indicates that the force is attractive
Answer:
The moment of inertia about the rotation axis is 117.45 kg-m²
Explanation:
Given that,
Mass of one child = 16 kg
Mass of second child = 24 kg
Suppose a playground toy has two seats, each 6.1 kg, attached to very light rods of length r = 1.5 m.
We need to calculate the moment of inertia
Using formula of moment of inertia


m = mass of seat
m₁ =mass of one child
m₂ = mass of second child
r = radius of rod
Put the value into the formula


Hence, The moment of inertia about the rotation axis is 117.45 kg-m²
The wires should be attached to each screw on the light not only one
Answer:

Explanation:
Additional information:
<em>The ball has charge </em>
<em>, and the ring has positive charge </em>
<em> distributed uniformly along its circumference. </em>
The electric field at distance
along the z-axis due to the charged ring is

Therefore, the force on the ball with charge
is


and according to Newton's second law

substituting
we get:

rearranging we get:

Now we use the approximation that
<em>(we use this approximation instead of the original </em>
<em> since </em>
<em>, our assumption still holds )</em>
and get


Now the last equation looks like a Simple Harmonic Equation

where

is the frequency of oscillation. Applying this to our equation we get:


The correct option is 0.5 M
Calculation
Wavelength is defined as the ratio of velocity of a wave to its frequency. It is measure in meters. Mathematically, wavelength is given by the following formula:
Wavelength = wave velocity / frequency
From the details given in the question,
Wavelength =?
Velocity = 340 m/s
Frequency = 680 HZ
Wavelength = 340 /680 = 0.5
Therefore, wavelength = 0.5 M