Matter. I don't really know how to explain it. Sorry. But anyways, Hope this helps!
Answer:
Electric force, 
Explanation:
Given that,
Electric charge 1, 
Electric charge 2, 
Distance, 
To find,
The electric force between these two sets of charges.
Solution,
There exists a force between two electric charges and this force is called electrostatic force. It is equal to the product of electric charged divided by square of distance between them.

k is the electrostatic constant


So, the electric force between these two sets of charges is
.
Answer:

Explanation:
let the ladder is of mass "m" and standing at an angle with the ground
So here by horizontal force balance we will have

by vertical force balance we have

now by torque balance about contact point on ground we will have

so we will have

now from first equation we have


D is not a scientific experiment.
Present day earth is in the Cenozoic era and the time period for it is 66 million years ago to today.