Scientists can tell this by looking at seismic waves released by earthquakes. ( if you need me to elaborate more ask)
Answer:
<h3>The answer is 5.4 kg</h3>
Explanation:
The mass of the object can be found by using the formula

f is the force
a is the acceleration
From the question we have

We have the final answer as
<h3>5.4 kg</h3>
Hope this helps you
Answer:
Expression of work done is

Work done to move the sled is given as 187.2 J
Explanation:
As we know that the formula of work done is given as

here we know that
F = 12.6 N
d = 15.4 m

so we will have


Answer:
Part 1 
Part 2 
Part 3 
Explanation:
Given
Number of protons 
Radius of nucleus 
Distance of the electrons 
Part 1
Electric field produced by just outside its surface

Part 2
Electric field produced by just outside its surface

Part 3
The net electric field inside a uniform shell of negative charge is zero because the electric flux lines cancel out each other
hence, the solution is
Part 1 
Part 2 
Part 3 
The circuit is no longer closed.