The initial mass of a radioactive substance is 20g. The substance has a half -life of 5 years. Determine the mass remaining after 20 years.

The initial mass of a radioactive substance is 20g. The substance has a half -life of 5 years. Determine the mass remaining after 20 years.

---

---

sharon kalunda answered the question on May 31, 2019 at 08:28

Exams With Marking Schemes

• Grade 1
• Grade 2
• Grade 3
• Grade 4
• Grade 5
• Grade 6
• Grade 7
• Grade 8
• Grade 9
• PP1
• PP2
• Playgroup
• Form 1
• Form 2
• Form 3
• Form 4

Related Questions

---

• The diagram below shows an arrangement of capacitors in a circuit. Determine:- (i) The total capacitance (ii) The total charge (iii) The energy stored by the 2µF... (Solved)
  

  The diagram below shows an arrangement of capacitors in a circuit.
  
  Determine:-
  (i) The total capacitance
  (ii) The total charge
  (iii) The energy stored by the 2μF capacitor.

  Date posted: May 31, 2019 .    Answers (1)

• Explain why carbon -14 is radioactive while Carbon -12 is not. (Solved)
  

  Explain why carbon -14 is radioactive while Carbon -12 is not.

  Date posted: May 31, 2019 .    Answers (1)

• The figure below shows an object O infront of a concave mirror and its image, I, formed after reflection. On the same diagram draw appropriate ray(s)... (Solved)
  

  The figure below shows an object O infront of a concave mirror and its image, I, formed after reflection.
  
  On the same diagram draw appropriate ray(s) to locate the principal focus F, of the mirror.

  Date posted: May 31, 2019 .    Answers (1)

• In figure shown below (not drawn to scale), sketch the path of a ray till it emerges from the prism. (Solved)
  

  In figure shown below (not drawn to scale), sketch the path of a ray till it emerges from the prism.
  

  Date posted: May 31, 2019 .    Answers (1)

• The figure below shows wave fronts approaching a concave sphere. Complete the diagram to show wave fronts formed after striking the surface. Show how focal point... (Solved)
  

  The figure below shows wave fronts approaching a concave sphere.
  
  Complete the diagram to show wave fronts formed after striking the surface. Show how focal point of the surface is located.

  Date posted: May 31, 2019 .    Answers (1)

• The figure below shows a displacement time graph for a wave motion. What is the frequency of the wave? (Solved)
  

  The figure below shows a displacement time graph for a wave motion.
  
  What is the frequency of the wave?

  Date posted: May 31, 2019 .    Answers (1)

• The plates of a simple cell are connected through a torch bulb and then dipped into dilute sulphuric acid on a beaker. The bulb lights brightly... (Solved)
  

  The plates of a simple cell are connected through a torch bulb and then dipped into dilute sulphuric acid on a beaker. The
  bulb lights brightly for a short time. State two possible causes of this.

  Date posted: May 31, 2019 .    Answers (1)

• The coil of an electric motor is usually wound on a soft iron armature. State two purposes of this armature. (Solved)
  

  The coil of an electric motor is usually wound on a soft iron armature. State two purposes of this armature.

  Date posted: May 31, 2019 .    Answers (1)

• A boy observes his face in a concave mirror of focal length 100cm. If the mirror is 80cm away, state one characteristic of the image... (Solved)
  

  A boy observes his face in a concave mirror of focal length 100cm. If the mirror is 80cm away, state one characteristic of the image observed.

  Date posted: May 31, 2019 .    Answers (1)

• The figure below shows the image behind a mirror M. By ray diagram construction, locate the position of the object. (Solved)
  

  The figure below shows the image behind a mirror M.
  
  By ray diagram construction, locate the position of the object.

  Date posted: May 31, 2019 .    Answers (1)

• Explain why a body moving in horizontal circular motion does no work. (Solved)
  

  Explain why a body moving in horizontal circular motion does no work.

  Date posted: May 31, 2019 .    Answers (1)

• A pendulum bob is raised to a height of 60cm above its lowest point and made to swing as shown in the figure. Determine the velocity... (Solved)
  

  A pendulum bob is raised to a height of 60cm above its lowest point and made to swing as shown in the figure.
  
  Determine the velocity of the mass at the height where kinetic energy is equal to the potential energy.

  Date posted: May 31, 2019 .    Answers (1)

• Figure below shows two rays of monochromatic light incident on two adjacent slits S1 and S2 State what is observed on the screen when the: i) Distance... (Solved)
  

  Figure below shows two rays of monochromatic light incident on two adjacent slits S1 and S2
  
  State what is observed on the screen when the:
  i) Distance X is increased.
  ii) Slit separation, d is reduced.
  iii) White light is used.

  Date posted: May 31, 2019 .    Answers (1)

• The wave shown in figure below has a velocity of 200m/s Determine i) The period T of the wave ii) The frequency of the wave. iii)... (Solved)
  

  The wave shown in figure below has a velocity of 200m/s
  
  Determine
  i) The period T of the wave
  ii) The frequency of the wave.
  iii) The wavelength of the wave.

  Date posted: May 31, 2019 .    Answers (1)

• A 200g mass of copper was heated to 100°C and then transferred to a lagged copper calorimeter of mass 5g containing 125g of water at... (Solved)
  

  A 200g mass of copper was heated to 100°C and then transferred to a lagged copper calorimeter of mass 5g containing 125g of water at 30°C. Calculate the final temperature of water. (Specific heat capacity of copper = 400J/KgK, water =4200J/KgK).

  Date posted: May 31, 2019 .    Answers (1)

• The figure (a) below shows a distance -time graph of a motion of a body.In the figure (b), sketch the corresponding velocity-time graph for the... (Solved)
  

  The figure (a) below shows a distance -time graph of a motion of a body.In the figure (b), sketch the corresponding velocity-time graph for the same motion.
  
  

  Date posted: May 31, 2019 .    Answers (1)

• The expression below is an equation for a radioactive element P. Element Q and R are the daughter nuclides. P, Q and R are not... (Solved)
  

  The expression below is an equation for a radioactive element P. Element Q and R are the daughter nuclides. P, Q and R are not the actual symbols of any of the elements.
  
  Identify the element R and state two of its characteristics.

  Date posted: May 31, 2019 .    Answers (1)

• The mass of the fabric of a large balloon is 100kg. The balloon is inflated with 200cm³ of helium. The balloon is attached to a... (Solved)
  

  The mass of the fabric of a large balloon is 100kg. The balloon is inflated with 200cm³ of helium. The balloon is attached to a cable fixed to the ground as shown.
  (Density of air and helium are 1.25kg/m³ and 0.2kg/m³ respectively)
  
  i) Indicate all the forces acting on the system.
  ii) If the system is at equilibrium, write an equation relating the three forces in (i) above.
  iii) Calculate the upthrust on the balloon.

  Date posted: May 31, 2019 .    Answers (1)

• Explain why most of the x-ray tube is surrounded by lead metal. (Solved)
  

  Explain why most of the x-ray tube is surrounded by lead metal.

  Date posted: May 31, 2019 .    Answers (1)

• Figure below shows circular waves approaching a plane barrier in uniform medium. On the diagram sketch the reflected waves. (Solved)
  

  Figure below shows circular waves approaching a plane barrier in uniform medium.
  
  On the diagram sketch the reflected waves.

  Date posted: May 31, 2019 .    Answers (1)