Home » 1. A radioactive isotope produces 1.00 x 105 disintegrations/minute. After 30 days,

# 1. A radioactive isotope produces 1.00 x 105 disintegrations/minute. After 30 days,

1. A radioactive isotope produces 1.00 x 105 disintegrations/minute. After 30 days, the sample produces only 1.00 x 104 disintegrations/minute. Knowing that radioactive decay is a first-order rate process, what is the half-life of this isotope?2. An implantable medical device for cardiac pacing has a sealed metal can containing electronics (typically called an implanted pulse generator – IPG). You are testing the seal on the can for water leakage. The maximum tolerable water level in the can is 25 g/cm3 of internal free volume (space not occupied by the electronics and battery). The IPG has a free internal volume of 2 cm3 . You undertake accelerated testing: at 80oC you measure a rate constant for leakage into the can of 10 pg/s(pg=picogram) and at 60oC a rate constant of 1 pg/s. The IPG is surgically replaced every ten years because the internal battery is exhausted. Can you tell your boss that the seal will last a minimum of twenty (20) years in the body (a safety factor of two)? You also know the concentration of water outside the IPG is constant and thus the leakage is independent of the starting water composition. Support your answer quantitatively.3. You are asked to prepare a phosphate buffer of pH 7.5. The total phosphate concentration in the buffer should be 0.1 M. a. How many grams of 2 4 (monobasic sodium phosphate, MW=120 g/mol) and 2 4 (dibasic sodium phosphate, MW=142 g/mol) are required to make 1 liter of the buffer?b. What is the pH of 100 ml of buffer from Part a, if 10 ml of 0.05 ml HCl (hydrochloric acid) are added to the 100 ml aliquot?4. You have designed a pressure vessel to operate with pure liquid water at a temperature range from above 100oC to 350oC. Based on the data provided in Figure 1 – equations and thermodynamic data – what is the maximum pH of the water that will be encountered in the pressure vessel over this operating temperature range? (Note that the water remains liquid over this temperature range due to the pressure inside the vessel).

At t = 0 a block with mass M = 5 kg moves with a
Question At t = 0 a block with mass M = 5 kg moves with a velocity v = 2 m/s at position xo = -.33 m from the equilibrium position of the spring. The block is attached to a massless spring of spring constant k = 61.2 N/m and slides on a frictionless surface. At what time will the block next pass x = 0, the place where the spring is unstretched?t1 =

1. Describe 3 different but specific examples where energy transforms
Question 1. Describe 3 different but specific examples where energy transforms from one type to another. A rock falling from a cliff is an example of gravitational potential energy transforming to kinetic (or mechanical) energy. Do not use any type of energy more than once in your examples and no credit for having anything falling since that was given as an example!). 2. Height at point A is 30.0 meters with a cart mass of 200.0 kg initially at rest. Point B is at a height of 25.0 meters. Find the KE and PE at points A and B along with the velocity at point B assuming no friction. 3. A 0.255 kg air-track glider moving at 1.25 m/s bumps into a 0.150 kg glider at rest. a.) Find the total kinetic energy after collision if the collision is elastic.b.) Find the change in kinetic energy after the collision if the collision is perfectly inelastic.Show all your work.

1. A 750.00 gram lead block absorbs heat to raise its
Question
1. A 750.00 gram lead block absorbs heat to raise its temperature from 20.0 degrees Celsius to 135.0 degrees Celsius. Using the table above, find the amount of heat energy in Joules that was required. Show your work.2.A 0.35 kg unknown substance absorbs 1.974 x 105J of heat to raise its temperature by 120 degrees C. What is the specific heat of this substance? Show your work. 3.You have a 320g block of silver at room temperature of 22 °C. Silver melts at 962°C. How much heat energy would be needed to just melt the silver? (Hf (silver) = 111 kJ/kg). Show all work.

Visible light passes through a diffraction grating that has 900 slits
Question Visible light passes through a diffraction grating that has 900 slits per centimeter, and the interference pattern is observed on a screen that is 2.34 mm from the grating.In the first-order spectrum, maxima for two different wavelengths are separated on the screen by 2.66 mm . What is the difference between these wavelengths? Express in meters.

a 2.00kg mass is moving in a circular path with a radius of 5.00cm.
Question a 2.00kg mass is moving in a circular path with a radius of 5.00cm. the mass starts from rest and with constant angular acceleration obtains an angular velocity of 6.00 rad/sec in 3.00sec. the mass then comes to a stop with constant angular acceleration in 4.00 sec. the radial component of acceleration of the mass at 2.00 sec is?

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