1. A 150 Newton horizontal force pushes a 20 kg mass sitting on a horizontal sur
ID: 2089655 • Letter: 1
Question
1. A 150 Newton horizontal force pushes a 20 kg mass sitting on a horizontal surface. Additionally, the horizontal surface exerts a 50 Newton frictional force on the mass. What is the acceleration of the mass? 3. Rhenium-186 is a beta emitter with weak gamma emission useful for imaging. If a sample has an initial activity of 18.0 Ci, what is the activity 19 days later? The half-life of rhenium-186 is 3.8 days. 5. A solution has a hydronium-ion concentration of 1.0 x 10-2 mol per liter. What is the pH of this solution? Is this solution acidic or basic? What is the hydroxide-ion concentration of this solution?Explanation / Answer
a =[150-50]/20 = 5 m/s^2
b) 19/3.8 = 5 half time so
activity after 19 days = (18/2^5)= 0.05625 Ci
C) ph = -log[H+]= -log(10^-2)
= 2 so ph< 7 solution is acidic
[H=][OH-]= 10^-14
[OH-]= 10^-12 mole per liter
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