Answer:
It takes
to accelerate the object from rest to the speed v.
Explanation:
From Newton's second law:
(1)
and the definition of acceleration,
(2)
we can solve this problem. Putting (2) in (1) we have:
and solving for
and considering the initial time as zero (
) and the initial velocity also zero (
) we have:

Now, for a mass
and the
we can wrtie the same equation:
and substituting
and
:

So now, it only takes half the time to accelerate the object from rest to the speed v
' D ' is the only correct statement on the list.
Electromagnetic waves are capable of traveling through
many substances, and they're also capable of traveling
through vacuum. Mechanical waves can't travel in vacuum.
The number of electrons is equal to the number of protons.
Answer: 
Explanation:
The equation to calculate the center of mass
of a particle system is:

In this case we can arrange for one dimension, assuming the geometric center of the Earth and the ladder are on a line, and assuming original center of mass located at the Earth's geometric center:

Where:
is the mass of the Earth
is the mass of 1 billion people
is the radius of the Earth
is the distance between the center of the Earth and the position of the people (2 m above the Earth's surface)

This is the displacement of Earth's center of mass from the original center.