when the depth of liquid in a container is x cm, the volume of the liquid is x(x^2+25) cm^3. Liquid is added to the container at a constant rate of 2 cm^3/s. Find the rate of change of the depth of the liquid at the instant when x=1
![Steve](/images/users/0/1/128x128.jpeg)
10 years ago
![tasha](/images/users/0/1/128x128.jpeg)
10 years ago
mr Steve, thus how i was given the question, jst like that without the shape of the container. Pliz hlp
![Steve](/images/users/0/1/128x128.jpeg)
10 years ago
hmmm. well, let's see. Ah, I see they gave the formula for the volume, so we don't have to derive it from the shape of the container.
v = x(x^2+25) = x^3 + 25x^2
dv/dt = (3x^2 + 50x) dx/dt
so,
2 = (3+50) dx/dt
dx/dt = 2/53
![Sara](/images/users/0/1/128x128.jpeg)
9 years ago
A little late but here is the answer:
You know that the rate of change of the volume is dV/dt = 2 (given in the question).
You also know that V = x^3 + 25x
To find the rate of change of the depth of the liquid, we find
dx/dt = dx/dV x dV/dt
dV/dx = 3x^2 + 25, so dx/dV is 1 over that
so dx/dt = 2 / (3x^2 + 25)
Pluggin in x = 11 into the equation, we get
dx/dt = 0.00515 cm/s
![Explain Bot](/images/users/4931/128x128.jpeg)
7 months ago
To find the rate of change of the depth of the liquid, we need to differentiate the equation that relates the depth (x) of the liquid to its volume.
Given: The volume of the liquid, V, is x(x^2+25) cm^3.
Differentiating both sides of this equation with respect to time (t), we get:
dV/dt = d/dt (x(x^2+25))
Now, let's differentiate each term separately using the product rule:
dV/dt = x d/dt (x^2+25) + (x^2+25) d/dt (x)
The derivative of x^2 with respect to time is 2x(dx/dt).
The derivative of 25 with respect to time is 0 since it is a constant.
dV/dt = x * 2x(dx/dt) + (x^2+25) dx/dt
Now, let's substitute dx/dt = 2 cm^3/s (because the liquid is added at a constant rate of 2 cm^3/s):
dV/dt = x * 2x(2) + (x^2+25) * 2
Simplifying further, we have:
dV/dt = 4x^2 + 2(x^2 + 25)
Next, we need to find the rate of change of the depth of the liquid at the instant when x=1. To do this, we substitute x=1 into our expression for dV/dt:
dV/dt = 4(1)^2 + 2((1)^2 + 25)
dV/dt = 4 + 2(1 + 25)
dV/dt = 4 + 2 + 50
dV/dt = 56 cm^2/s
Therefore, the rate of change of the depth of the liquid at the instant when x=1 is 56 cm^2/s.