Answer:
3
Explanation:
The half-life of a radioactive isotope is the time it takes for the mass of the sample to halve.
This can be rewritten as follows:
where
m(t) is the mass of the sample at time t
m0 is the original mass of the sample
n is the number of half-lives that passed
We see that if we take n=3, the amount of original sample left is
So 3 (3 half-lives) is the correct answer.
Energy cannot be created nor be destroyed
Spectroscopy — the use of light from a distant object to work out the object is made of — could be the single-most powerful tool astronomers use, says Professor Fred Watson from the Australian Astronomical Observatory. ... "It lets you see the chemicals being absorbed or emitted by the light source.
Answer:
The forces creating the net force must lie in the same direction.
Explanation:
newton's second law states that the net force acting on the body is equal to the product of mass and the acceleration of the body.
If there are several forces acting on the body in different directions, then we have to find teh net force by using the vector sum and then find the acceleration.
It is not necessary that all the forces acting in the same direction.
if they are in different directions then we have to find the net force by t=using the formula for the vector sum.