Answer:
q₁ = -6.54 10⁻⁵ C
Explanation:
Force is a vector quantity, but since all charges are on the x-axis, we can work in one dimension, let's apply Newton's second law
F = F₁₂ + F₂₃
the electric force is given by Coulomb's law
F = k q₁q₂ / r₁₂²
let's write the expression for each force
F₂₃ = k q₂ q₃ / r₂₃²
F₂₃ = 9 10⁹ 34.4 10⁻⁶ 72.8 10⁻⁶ / 0.1²
F₂₃ = 2.25 10³ N
F₁₂ = k q₁q₂ / r₁₂²
F₁₂ = 9 10⁹ q₁ 34.4 10⁻⁶ / 0.1²
F₁₂ = q₁ 3,096 10⁷ N
we substitute in the first equation
225 = q₁ 3,096 10⁷ +2.25 10³
q₁ = (225 - 2.25 10³) / 3,096 10⁷
q₁ = -6.54 10⁻⁵ C
I assume L=120 yards as the length of the football field.
1) The average speed is given by the total distance covered by the player divided by the time taken.
The total distance covered to go from one goal line to the other and then back to the 40-yards line is

And the time taken is t=22.4 s, so the average speed of the player is

2) The find the average velocity, we should also consider the direction (and the sign) of the velocity.
In the the first part of the motion, the player goes from one goal line to the other one, so he covers 120 y. However, in the second part of the motion he goes back by 80 y. Therefore, the net displacement of the player is

and so, the average velocity is
1. Single dental x-rays: 
The energy of the photon is

Using the conversion factor

we can convert it into Joules:

The relationship between photon energy and wavelength is

where
is the Planck constant
is the speed of light
E is the energy
Substituting into the formula, we find

2. Microtomography: 
The energy of these photons is 2.5 times greater, so

And by applying the same formula used at point 1, we find the corresponding wavelength:

Answer:
A. The starting height of the ball
Explanation:
When we talk about controlled variables, we refer to the variable that should be kept the same throughout the experiment. The reason why we do this, is to limit anything else that is not being tested, that may affect the results of the experiment.
In the scenario given, the experiment is to see the relationship between the <u>initial height of a basketball</u> and the <u>height of its rebound bounce. </u>
So you the starting height of the ball should vary, meaning it is NOT controlled.
Answer:
velocity = 0.3m/s
speed = 1.21 m/s
Explanation:
The total time it takes to get from the front door to the bench is
t = 27 + 39 = 66 seconds
The net displacement from the front door to the bench is the distance from the front door to the windmill subtracted by the distance from the windmill to the bench
s = 50 - 30 = 20 m
So the average velocity is net displacement divided by total time
v = s / t = 20 / 66 = 0.3 m/s
The total distance from the front door to the bench is the sum of distance from the front door to the windmill and the distance from the windmill to the bench
S = 50 + 30 = 80 m
So the average speed is total distance divided by total time
v = s / t = 80 / 66 = 1.21 m/s