Answer:
Gravity, also called gravitation, in mechanics, the universal force of attraction acting between all matter. ... On Earth all bodies have a weight, or downward force of gravity, proportional to their mass, which Earth's mass exerts on them. Gravity is measured by the acceleration that it gives to freely falling objects
1 : A force of attraction that tends to draw particles or bodies together.
2 : The attraction of bodies by the force of gravity toward the center of the earth.
3 : Great seriousness.
Via half-life equation we have:

Where the initial amount is 50 grams, half-life is 4 minutes, and time elapsed is 12 minutes. By plugging those values in we get:

There is 6.25 grams left of Ra-229 after 12 minutes.
Answer:
4.4 square meters = 47 square foot
Explanation:
We have
1 meter = 3.28084 foot
1 square meter = 3.28084 x 3.28084 square foot = 10.76 square foot
4.4 square meters = 4.4 x 10.76 = 47.36 square foot = 47 square foot
4.4 square meters = 47 square foot
Answer:
The friction force is 250 N
Explanation:
The desk is moving at constant velocity. This means that its acceleration is zero: a = 0. Newton's second law states that the resultant of the forces acting on the desk is equal to the product between mass (m) and acceleration (a):

In this case, we know that the acceleration is zero: a = 0, so also the resultant of the forces must be zero:
(1)
We are only interested in the forces acting along the horizontal direction, since it is the direction of motion. There are two forces acting in this direction:
- the pull, forward, F = 250 N
- the friction force, backward, 
Given (1), we have

So the force of friction must be equal to the pull:

Answer:
William Gilbert
Explanation:
first described the Earth as a giant dipole magnet 400 years ago. But, as Rod Wilson recounts, he did far more than this.