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2) 0.01moles of an ideal diatomic gas is enclosed in an adiabatic cylinder of cross-sectional area A=10-4m2.In the arrangement shown,a block of mass m=1kg is suspended from a spring of stiffness constant k=16N/m.Initially,the spring is relaxed and the volume of the gas is V=1.4 X 10-4m3.

(a)Find the initial pressure of the gas?

(b)If block m is gently pushed down and released it oscillates harmonically,find its angular frequency of oscillation.

(c)When the gas in the cylinder is heated up the piston starts moving up and the spring gets compressed so that block M is just lifted up.Determine the heat supplied.Take atmospheric pressure p0=105 Nm-2,g=10 ms-2.

Hrishant Goswami , 12 Years ago
Grade 10
anser 1 Answers
Askiitians Tutor Team

To tackle this problem, we need to break it down into manageable parts. We have an ideal diatomic gas in an adiabatic cylinder, a spring, and a block. Let's address each part of the question systematically.

Finding the Initial Pressure of the Gas

We can use the ideal gas law to find the initial pressure of the gas. The ideal gas law is expressed as:

P V = n R T

Where:

  • P = pressure of the gas
  • V = volume of the gas
  • n = number of moles of gas
  • R = universal gas constant (approximately 8.314 J/(mol·K))
  • T = absolute temperature in Kelvin

Since we are not given the temperature, we can assume standard conditions (T = 273 K) for simplicity. Given:

  • n = 0.01 moles
  • V = 1.4 x 10-4 m3

Substituting the values into the ideal gas law:

P = (n R T) / V

Calculating:

P = (0.01 moles * 8.314 J/(mol·K) * 273 K) / (1.4 x 10-4 m3)

P ≈ 1.73 x 105 N/m2

Angular Frequency of Oscillation

Next, we need to determine the angular frequency of the oscillation of the block attached to the spring. The angular frequency (ω) for a mass-spring system is given by:

ω = √(k/m)

Where:

  • k = spring constant (16 N/m)
  • m = mass of the block (1 kg)

Substituting the values:

ω = √(16 N/m / 1 kg) = √16 = 4 rad/s

Calculating the Heat Supplied

When the gas is heated, it expands and does work on the piston, lifting the block. To find the heat supplied (Q), we can use the first law of thermodynamics:

Q = ΔU + W

Where:

  • ΔU = change in internal energy
  • W = work done by the gas

For an ideal diatomic gas, the change in internal energy can be calculated as:

ΔU = n Cv ΔT

Here, Cv for a diatomic gas is approximately 5R/2. However, we need to find the temperature change (ΔT) when the gas expands to lift the block. The work done by the gas can be calculated as:

W = P ΔV

To lift the block, the force exerted by the gas must equal the weight of the block:

P A = m g

Substituting the values:

P (10-4 m2) = (1 kg)(10 m/s2)

From our previous calculation, we can find the change in volume (ΔV) as the gas expands. However, since we need to find the heat supplied, we can rearrange the equation:

Q = m g h + n Cv ΔT

Assuming the height (h) the block is lifted is small, we can approximate the heat supplied based on the work done against gravity and the internal energy change. The exact values will depend on the specific conditions of the gas and the temperature change.

In summary, we have:

  • Initial pressure of the gas: 1.73 x 105 N/m2
  • Angular frequency of oscillation: 4 rad/s
  • Heat supplied: Depends on ΔT and work done

This breakdown should help clarify each part of the problem. If you have any further questions or need more details on any specific part, feel free to ask!

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