The mass of Actinium 227 left is 0.0078 kg
Explanation:
The amount of mass left of a radioactive isotope after time t is given by the equation:

where
is the initial amount of the sample
t is the time
is the half-life of the isotope
For the sample of Actinium 227 in this problem,


t = 160 years
Substituting into the equation,

#LearnwithBrainly
Explanation:
U = 40m/s
V = 30m/s
T = 5 sec
A = ?




since it's decreasing in speed, The acceleration will be " - 2.0ms^-2 " or " - 2.0m/s^2 "
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C. the same as when it was at the top of its path
Answer: A-they change the direction of the forces
Explanation:
Any device which makes our work simpler is known as a machine. A machine may increase the amount of output force which is determined by its mechanical advantage or a machine changes the direction of the force.
In the given situation the input force acts in the downward direction to pull the rope. The output force acts on the flag being pulled upwards at the other end. Thus, the direction of the forces varies. Correct option is A.