Radioactive decay is given by:
N = No x e^(-λt)
We know that N/No has to be 0.05
λ = 0.15
0.05 = e^(-0.15t)
t = ln(0.05)/(-0.15)
t = 19.97 days
3750 seconds to travel that far
Answer:
5) Displacement = +3.125 m
Displacement is in the same direction as the force vector.
6) Force = -53.89 N
Force is in an opposite direction relative to the displacement.
Explanation:
5) We are given;
Force; F = 160 N.
Workdone; W = +500 J
Now, formula for workdone is;
W = Force × displacement
Thus, displacement = Work/force
Displacement = 500/160
Displacement = +3.125 m
Thus, displacement is in the same direction as the force vector.
6) We are given;
Displacement; d = 18 m.
Workdone; W = -970 J
Like in the first answer above,
Workdone = Force × Displacement
Thus;
Force = Workdone/Displacement
Force = -970/18
Force = -53.89 N
Since force is negative and displacement is positive, it means force is in an opposite direction relative to the displacement.
Normally, the water pressure inside a pump is higher than the vapor pressure: in this case, at the interface between the liquid and the vapor, molecules from the liquid escapes into vapour form. Instead, when the pressure of the water becomes lower than the vapour pressure, molecules of vapour can go inside the water forming bubbles: this phenomenon is called
cavitation.
So, cavitation occurs when the pressure of the water becomes lower than the vapour pressure. In our problem, vapour pressure at

is 1.706 kPa. Therefore, the lowest pressure that can exist in the pump without cavitation, at this temperature, is exactly this value: 1.706 kPa.