Calculate work done in a PV process

PhysicsThermodynamicsMediumSTEM

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Q.3. Find the work done using this graph.

This question includes visual content: A Cartesian coordinate system graph. The y-axis is labeled $V(m^3)$ and the x-axis is labeled $P(N/m^2)$. A straight line segment with an arrow pointing towards B starts at point A and ends at point B. Point A has coordinates $(2, 6)$ and point B has coordinates $(10, 14)$. Dashed lines connect these points to the axes at values 2 and 10 on the P-axis, and 6 and 14 on the V-axis.

Animated Video Solution

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Step by Step Written Solution

1
Step 1

Hi Mohammad, let's solve this work done problem step by step using the graph.

Reading the Graph

From the graph, point A is at pressure $2\;\text{N/m}^2$ and volume $6\;\text{m}^3$. Point B is at pressure $10\;\text{N/m}^2$ and volume $14\;\text{m}^3$.

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Step 2

Notice that the graph has pressure on the horizontal axis and volume on the vertical axis. For a pressure-volume graph, the work done equals the area under the curve.

$$W=\int P\,dV$$
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Step 3

Since the path from A to B is a straight line, we can use the average pressure multiplied by the change in volume.

$$W=P_{\text{avg}}\Delta V$$
$$P_{\text{avg}}=\frac{P_1+P_2}{2}$$
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Step 4

Now let's calculate the average pressure and the change in volume.

Substitution Step

$$P_1=2\;\text{N/m}^2,\quad P_2=10\;\text{N/m}^2$$
$$\Delta V=14-6=8\;\text{m}^3$$
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Step 5

The average pressure is two plus ten over two, which gives six newtons per meter squared.

$$P_{\text{avg}}=\frac{2+10}{2}=6\;\text{N/m}^2$$
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Step 6

Now substitute the values into the work formula.

$$W=6\times 8$$

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About This Question

Subject
Physics
Topic
Thermodynamics
Difficulty
Medium
Exam
STEM
Question Type
Open Ended

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