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Question

A rocket motor consumes $3000\text{ kg}$ of fuel per minute exhausting it with a speed of $5 \times 10^{3}\text{ m/s}$. The magnitude of force exerted on rocket is :

The correct answer is
$25 \times 10^{4}\text{ N}$

Rocket Thrust Force Calculation

The force exerted on a rocket is called thrust. It arises from the momentum change of the expelled exhaust gases. The magnitude of this force can be calculated using the principle of momentum conservation.

Physics Principle

The thrust force ($F$) is equal to the rate at which momentum is carried away by the exhaust gases. Mathematically, this is expressed as:

$ F = \left| v_e \frac{dm}{dt} \right| $

Where:

  • $v_e$ is the exhaust velocity of the gases.
  • $\frac{dm}{dt}$ is the rate of fuel consumption (mass expelled per unit time).

Given Data

  • Fuel consumption rate: $3000\text{ kg/min}$
  • Exhaust speed ($v_e$): $5 \times 10^{3}\text{ m/s}$

Unit Conversion

The fuel consumption rate must be converted from kg/min to kg/s to be consistent with the SI unit of velocity (m/s).

$ \frac{dm}{dt} = \frac{3000\text{ kg}}{1\text{ min}} \times \frac{1\text{ min}}{60\text{ s}} = \frac{3000}{60}\text{ kg/s} = 50\text{ kg/s} $

Force Calculation

Now, substitute the values into the thrust formula:

$ F = (5 \times 10^{3}\text{ m/s}) \times (50\text{ kg/s}) $

$ F = 250 \times 10^{3}\text{ kg}\cdot\text{m/s}^2 $

Since $1\text{ N} = 1\text{ kg}\cdot\text{m/s}^2$, the force is:

$ F = 250 \times 10^{3}\text{ N} $

To express this in scientific notation similar to the options:

$ F = 25 \times 10^{1} \times 10^{3}\text{ N} = 25 \times 10^{4}\text{ N} $

Conclusion

The magnitude of the force exerted on the rocket is $25 \times 10^{4}\text{ N}$.

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Important Questions from Miscellaneous

  1. Which of the following relationships is/are not true?
    (A). Most probable velocity = $\sqrt{\frac{2RT}{M}}$
    (B). PV = $\frac{3}{2}kT$
    (C). Compressibility factor Z = $\frac{pV}{nRT}$
    (D). Average kinetic energy of gas = $\frac{1}{2}kT$
    Choose the correct answer from the options given below
  2. Match List-I with List-II
    List-IList-II
    Electronic ConfigurationFirst Ionisation energy (kJ mol$^{-1}$)
    (A). ns$^2$(I). 2100
    (B). ns$^2$np$^1$(II). 1400
    (C). ns$^2$np$^3$(III). 800
    (D). ns$^2$np$^6$(IV). 900

    Choose the correct answer from the options given below:
  3. The shielding constant of a 2p electron (calculated using Slater's rules) is
  4. Match List-I with List-II
    List-IList-II
    SpectroscopyProperty
    (A). Raman(I). Polarizability
    (B). FTIR(II). Dipole Moment
    (C). UV-Visible(III). Absorbance
    (D). NMR(IV). Spin

    Choose the correct answer from the options given below:
  5. The structure of protein comprises of:
    (A). Primary structure of protein is associated with amino acids
    (B). Secondary structure of protein is associated to peptides
    (C). Tertiary structure of protein is associated with polypeptide chains
    (D). Quaternary structure of protein is associated with polypeptide chains
    Choose the correct answer from the options given below:
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