Answer:
B. 3
Explanation:
The half-life of a radioisotope is the time it needs for the mass of the radioisotope to halve with respect to its original value.
In this problem, the initial mass of the radioisotope at t=0 is
m0 = 50.0 mg
We see that after t = 1 min, the mass of the isotope is
m(1 min) = 25.0 mg
so, exactly half the initial mass: this means that 1 minute is exactly the half-life of this radioisotope.
So, the amount of mass left after each minute is the following:
m (1 min ) = 25.0 mg (1 half-life)
m (2 min) = 12.5 mg (2 half-lives)
m (3 min) = 6.25 mg (3 half-lives)
so, when we are left with 6.25 mg of isotope, 3 minutes have passed, which means that 3 half-lives have passed.
Answer:
B) is downward
Explanation:
The acceleration is always downward, because it is the gravitational acceleration.
When the ball is going up the acceleration is opposing the movement, and when the ball is going down the velocity has the same direction as the acceleration
Answer:
They land at the same time.
Explanation:
Two masses falling through a vacuum (no air resistance or buoyancy forces) will accelerate at the same rate when dropped from the same height. Therefore, despite having different masses, they land at the same time.
