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liq [111]
3 years ago
4

Let q(t) represent the amount of a certain reactant present at time t. suppose that the rate of decrease of q(t) is proportional

to q3(t). that is, q =−kq3, where k is a positive constant of proportionality. how long will it take for the reactant to be reduced to one half of its original amount? recall that, in problems of radioactive decay where the differential equation has the form q =−kq, the half-life was independent of the amount of material initially present. what happens in this case? does half-life depend on q(0), the amount initially present?
Physics
1 answer:
MakcuM [25]3 years ago
8 0

The rate of change is mathematically described as :

d(q(t))/dt = -kq(t)^3

using variable seperation bring d(q) and all functions of q to one side and dt and all functions of t to the other side. It should look like this:

\frac{d((t))}{q^3} = -k.dt

Now integrate on both sides.

-0.5q(t)^-2 = -kt - C

where C is constant of integration. Its value can be found using initial condition by simply putting  t=0 in the above equation

C =  1/2q(0)

After some algebraic simplification q(t) can be written as :

q(t)^2  = \frac{q(0)^2}{2q(0)^2Kt + 1}

at half time, q(T) = q(0)/2, where T = half time of reaction.

substitute this in the above equation:

T = \frac{3}{2Kq(0)^2}

This is the required solution. As can be seen half time (T) depends on K and q(0) that is the initial concentration.


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3 years ago
Which would produce mechanical waves?
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The answer is C. Hope this helped!
4 0
3 years ago
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The components of vector A are:
Korvikt [17]

here as it is given that x component of the vector is positive while y component of the vector is negative so we can say the vector must inclined in Fourth quadrant.

So angle must be more than 270 degree and less than 360 degree

Now in order to find the value we can say that

tan\theta = \frac{opposite\: side}{adjacent\: side}

tan\theta = \frac{8.6}{6.1}

\theta = tan^{-1}1.41

\theta = 54.65^0

so it is inclined at above angle with X axis in fourth quadrant

Now if angle is to be measured counterclockwise then its magnitude will be

\theta = 360 - 54.65 = 305.3^0

so the correct answer will be 305 degree

3 0
4 years ago
I have a set of calipers that can measure thickness of a few inches with an uncertainty of ±0.005 inches. I measure the thicknes
Shtirlitz [24]

Answer:

(a) 0.0113 ±0.0001 inches

(b) 5 decks

Explanation:

<u>Given information</u>

52 cards, thickness is 0.590 ±0.005 inches

Since this is thickness of all the cards, to get the thickness of a single card we divide the total thickness (plus uncertainty) by the number of cards hence

1 card=\frac {0.590}{52}±\frac {0.005}{52}= 0.0113461 ±0.000096 inches

Considering that thickness is given to 3 significant figures while uncertainty is to 1 significant figure, the final answer should also conform to these hence giving the first part of the answer to 3 significant figures while second part to 1 significant figure yields 0.0113 ±0.0001 inches

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Considering that the cards have uncertainty of 0.0001 inches and the number of decks, n required to create uncertainty of 0.00002 inch is given by

n=\frac {0.0001}{0.00002}=5

We need 5 decks for the given uncertainty

4 0
4 years ago
A ladder of length L is placed against a smooth wall such that it forms a angle θ with the wall and the friction force between t
GarryVolchara [31]

Answer:

a. m=\frac{2f_{s}tan\theta}{g}

b. m=5.99kg

Explanation:

a.

In order to solve this problem, we can start by drawing a diagram of the situation. Drawing a diagram is really important since it will help use understand the problem better and analyze it as well. (See attached picture).

In the diagram we can see the forces that are acting on the ladder. We will assume the ladder is static (this is it doesn't have any  movement) and analyze the respective forces in the x-direction and the forces in the y-direction, as well as the moments about point B.

So we start with the sum of forces about y, so we get:

\sum F_{y}=0

N-W=0

N=W

N=mg

Next we can do the sum of forces about x, so we get:

\sum F_{x}=0

which yields:

f_{s}-F_{W}=0

so:

f_{s}=F_{W}

Next the torque about point B, so we get:

\sum M_{B}=0

so:

f_{s} L sin\theta - NLcos\theta + \frac{WL}{2}cos\theta = 0

From the sum of forces in the y-direction we know that N=mg (this is because the wall makes no friction over the ladder) so we can directly substitute that into our equation, so we get:

f_{s} L sin\theta - WLcos\theta + \frac{WL}{2}cos\theta = 0

We can now combine like terms, so we get:

f_{s} L sin\theta -\frac{WL}{2}cos\theta = 0

we know that W=mg, so we can substitute that into our equation, so we get:

f_{s} L sin\theta -\frac{mgL}{2}cos\theta = 0

which can now be solved for the mass m:

\frac{mgL}{2}cos\theta = f_{s} L sin\theta

If we divided both sides of the equation into L, we can see that the L's get cancelled, so our equation simplifies to:

\frac{mg}{2}cos\theta = f_{s}sin\theta

we can now divide both sides of the equation into g so we get:

\frac{m}{2}cos\theta = \frac{f_{s}sin\theta}{g}

next we can divide both sides of the equation into cos θ so we get:

\frac{m}{2}= \frac{f_{s}sin\theta}{g cos\theta}

and finally we can multiply both sides of the equation by 2 so we get:

m=\frac{2f_{s}sin\theta}{g cos\theta}

we know that:

tan \theta=\frac{sin \theta}{cos \theta}

so we can simplify the equation a little more, so we get:

m=\frac{2f_{s}tan \theta}{g}

b.

So now we can directly use the equation to find the mass of the ladder with the data indicated by the problem:

θ=32° and f_{s}=47N

we also know that g=9.8m/s^{2}

so we can use our equation now:

m=\frac{2f_{s}tan \theta}{g}

so we get:

m=\frac{2(47N)tan (32^{o})}{9.8m/s^{2}}

which yields:

m=5.99kg

6 0
3 years ago
Read 2 more answers
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