No they all don't need a medium to travel.
Example is electromagnetic waves which travel through vacuum.
The maximum upward acceleration that the elevator can have without breaking is = 10.36m/s².
<h3>How to calculate maximum upward acceleration?</h3>
To calculate the maximum acceleration of the elevator we must take into account Newton's second law and its formula that takes into account the following aspects:
- F = Is the force applied in newtons.
- m = Is the mass of the object in kilograms.
- a = Is the acceleration of the object in meters per second squeared.
According to the above, we apply the values we have as follows:
- a =

- a =

Note: This question is incomplete because some information is missing. Here is the complete information.
Learn more about acceleration in: brainly.com/question/13312735
The distance from observer A of intensity of sound 59 db is 28.64 m and the distance from observer B of intensity of sound 83 db is 11.36m
Explanation:
Let's solve this problem in parts
let's start by finding the intensity of the sound in each observer
observer A β = 59 db
β = 
where I₀ =
W / m²

=
W / m²
Similarly for Observer b 
now we use that the emitted power that is constant is the intensity over the area of the sphere where the sound is distributed
P = I A
therefore for the two observers
the area of a sphere is

we substitute the above formula, we get
Let us call the distance from the observer A be to stereo speaker = x, so the distance from the observer B to the stereo speaker = 40- x; we substitute

after solving the above equation we get x = 28.64 m
This is the distance of observer A
similarly The distance from observer B is 35 - x
= 40 - 28.64
= 11.36m
To know more about intensity of sound with the given link
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It's a bit of a trick question, had the same one on my homework. You're given an electric field strength (1*10^5 N/C for mine), a drag force (7.25*10^-11 N) and the critical info is that it's moving with constant velocity(the particle is in equilibrium/not accelerating).
<span>All you need is F=(K*Q1*Q2)/r^2 </span>
<span>Just set F=the drag force and the electric field strength is (K*Q2)/r^2, plugging those values in gives you </span>
<span>(7.25*10^-11 N) = (1*10^5 N/C)*Q1 ---> Q1 = 7.25*10^-16 C </span>