1answer.
Ask question
Login Signup
Ask question
All categories
  • English
  • Mathematics
  • Social Studies
  • Business
  • History
  • Health
  • Geography
  • Biology
  • Physics
  • Chemistry
  • Computers and Technology
  • Arts
  • World Languages
  • Spanish
  • French
  • German
  • Advanced Placement (AP)
  • SAT
  • Medicine
  • Law
  • Engineering
garik1379 [7]
3 years ago
13

A radioactive substance decays according to the formula w = 20e¡kt grams where t is the time in hours. a find k given that after

50 hours the weight is 10 grams. b find the weight of radioactive substance present at: i t = 0 hours ii t = 24 hours iii t = 1 week. c how long will it take for the weight to reach 1 gram? d find the rate of radioactive decay at: i t = 100 hours ii t = 1000 hours. e show that dw dt is proportional to the weight of substance remaining.
Physics
1 answer:
blagie [28]3 years ago
5 0
W=20 e(-kt)  
A. Rearranging gives k= -(ln(w/20)/t 
 Substituting w= 10 and solving gives k=0.014 
 B. Using W=20e(-kt). After 0 hours, W=20. After 24 hours, W=14.29g. After 1 week (24x7=168h) W=1.9g 
 C. Rearranging gives t=-(ln(10/20)/k. Substituting w=1 and solving gives t=214 hours. 
 D. Differentiating gives dW/ dt = -20ke(-kt). Solving for t=100 gives dW/dt = 0.07g/h. Solving for t=1000 gives 0.0000002g/h 
 E. dW/dt = -20ke(-kt). But W=20e(-kt) so dW/dt = -kW
You might be interested in
Which of the following has more inertia?? bowling ball , hammer, Tennis ball feather
I am Lyosha [343]
The bowling ball would have the most inertia because it has the most mass. Inertia is the ability to resist a change in motion. So, it sort of makes sense that the more massive an object, the more resistance it has against outside forces. 
Bowling ball would be your answer since it has the most mass.
5 0
3 years ago
Identify two factors you must know to describe the motion of an object along a straight line
Sveta_85 [38]

In order to describe motion along a straight line, you must state the speed and direction of the motion. Those two quantities, together, comprise what's known as "velocity".

6 0
3 years ago
15. A body moving with a velocity of 20 m/s begins to accelerate at 3 m/s2. How far does the body move in 5 seconds? A. 137.5 m
Rudik [331]

Answer is B. According to the equation of motion s = vt + 1/2 at2 Where s is distance covered, v is velocity, a is acceleration and t is time taken. So, by putting all the values, we get s = (20)(5) + 1/2 (3)(5)2 s = 100 + 1/2 (3)(25) s = 100 + 1/2 75 s = 100 + 37.5 s = 137.5 meters



7 0
3 years ago
Read 2 more answers
Diabetes occurs when there is a large amount of sugar in the blood. Which gland is most likely not functioning well enough in a
elena-14-01-66 [18.8K]
C pancreas! i think it should be
5 0
3 years ago
Being overweight or obese increases the risk of:
Svetradugi [14.3K]

theanswer is b.heart disease

3 0
3 years ago
Read 2 more answers
Other questions:
  • This type of heat transfer occurs when heat moves from one molecule to another.
    5·2 answers
  • How do i explain to kids how much water on earth is drinkable?
    7·1 answer
  • What would be the best method for a scientist to use in order to obtain a precise measurement of star’s distance from Earth?
    7·2 answers
  • A 1-kilogram ball has 8 joules of kinetic energy.What is it speed?
    11·1 answer
  • What does the electron do in an atom?
    12·1 answer
  • "A 0.4 kg mass, attached to the end of a 0.75 m string, is whirled around in a circular horizontal path. If the maximum tension
    6·2 answers
  • What is the force of gravity between a 500kg bal and a 100,000kg basket 5m apart?
    7·2 answers
  • Which of the following sentences does not contain a type of variation?
    10·2 answers
  • What is the net force on a water bottle?
    11·2 answers
  • A sample from a meteorite that landed on Earth has been analyzed, and the result shows that out of every 1,000 nuclei of potassi
    6·1 answer
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!