A heat engine absorbs 500 J of heat and does 200 J of work. The heat rejected is:

The correct answer is B: 300 J. By energy conservation: Q_in = W + Q_out, so Q_out = Q_in - W = 500 - 200 = 300 J.

A reversible engine and an irreversible engine operate between the same two temperatures. Which has greater efficiency?

The correct answer is A: Reversible engine. Carnot (reversible) engine has maximum efficiency between any two temperatures. All real irreversible engines are less efficient.

For a gas obeying van der Waals equation, internal energy depends on:

The correct answer is C: Both temperature and volume. For van der Waals gas, U depends on both T and V because intermolecular forces depend on volume. For ideal gas, U depends on T only.

For a reversible adiabatic process of an ideal diatomic gas (γ = 1.4), if pressure increases from 1 atm to 10 atm, the temperature ratio T_f/T_i is:

The correct answer is A: 10^0.286. For adiabatic process: T·P^(1-γ)/γ = constant, so T_f/T_i = (P_f/P_i)^((γ-1)/γ) = 10^(0.4/1.4) = 10^(2/7) ≈ 10^0.286

The coefficient of performance (COP) of a refrigerator is 5. If 100 J of work is done on it, how much heat is removed from the cold reservoir?

The correct answer is B: 500 J. COP = Q_cold/W. Therefore, Q_cold = COP × W = 5 × 100 = 500 J

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NEET Physics

Physics questions for NEET UG — Mechanics, Thermodynamics, Optics, Modern Physics.

72 Q 3 Topics Take Mock Test

Difficulty: All Easy Medium Hard 71–72 of 72

Topics in NEET Physics

All Mechanics & Laws of Motion 100 Thermodynamics 100 Optics 1

Q.71 Easy Mechanics & Laws of Motion

If the mass of an object is doubled and the force applied remains the same, how does the acceleration change?

A Doubles

B Becomes half

C Remains same

D Becomes four times

Correct Answer: B. Becomes half

EXPLANATION

From Newton's second law, F = ma. If F is constant and m doubles, then a = F/2m, so acceleration becomes half.

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Q.72 Easy Mechanics & Laws of Motion

A body is moving with a constant velocity of 10 m/s. What is the net force acting on it?

A 0 N

B 10 N

C 100 N

D Cannot be determined

Correct Answer: A. 0 N

EXPLANATION

According to Newton's first law, when velocity is constant, acceleration is zero. Therefore, net force F = ma = m × 0 = 0 N.

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