Answer: Force = 81 N
Explanation:
from Columbs law,
F = k(q1*q2)/r²
k = 9 x 10^9 Nm²/C²
F = (9 x 10^9)x (0.9x10^-5 x 2.5x10^-4)/(0.5)²
F = 81 Newtons
By definition, we have that the work done is given by:

Where,
F: force in the direction of displacement
d: displaced distance
Substituting values we have:

Then, the power is given by:

Where,
t: time
Substituting values we have:


Answer:
The work done on the box is 100 Nm, and the power is 20 Nm/s.
C. Quarts watches is the correct answer
Answer: Convention
Explanation: Convention is pretty well known for being a process that transmits heat from one place to another place with the movements of heated particles. I got this answer from my notebook during my chemistry class.
Hope this answer helps!
To develop this problem we will apply the considerations made through the concept of Doppler effect. The Doppler effect is the change in the perceived frequency of any wave movement when the emitter, or focus of waves, and the receiver, or observer, move relative to each other. At first the source is moving towards the observer. Than the perceived frequency at first

Where F is the actual frequency and v is the velocity of the ambulance
Now the source is moving away from the observer.

We are also so told the perceived frequency decreases by 11.9%



Equating,





Solving for V,
