AQA A LEVEL PHYSICS 7408/3BC – ENGINEERING PHYSICS 2025: FULL 1–50 QUESTIONS WITH ANSWERS & EXPLANATIONS

AQA A LEVEL PHYSICS 7408/3BC –
ENGINEERING PHYSICS 2025:
FULL 1–50 QUESTIONS WITH
ANSWERS & EXPLANATIONS

AQA A-Level Physics 7408/3BC: Engineering Physics A flywheel of moment of inertia




1. Angular Impulse is equal to the change in:
A. Angular Velocity
B. Torque
C. Angular Momentum
D. Moment of Inertia
Answer: C
Rationale: Impulse



. This is the rotational equivalent of Linear Impulse (



).

2. In a 4-stroke petrol engine, the "Indicated Power" is:
A. The power delivered to the wheels
B. The power generated by the combustion of fuel in the cylinder
C. The power lost to friction
D. The power used by the alternator
Answer: B
Rationale: Indicated power is calculated from the p-V indicator diagram before accounting
for mechanical losses.

3. "Mechanical Efficiency" of an engine is the ratio of:
A. Brake Power to Indicated Power
B. Indicated Power to Fuel Power
C. Work Out to Heat In
D. Output Torque to Input Force
Answer: A
Rationale: Mechanical efficiency (

,) accounts for power lost to friction within the engine itself.

4. In an "Isochoric" process, which variable remains constant?
A. Pressure
B. Temperature
C. Volume
D. Entropy
Answer: C
Rationale: Isochoric (or isovolumetric) means the volume of the gas does not change, so



.

5. A process where pressure remains constant is called:
A. Isentropic
B. Isobaric
C. Adiabatic
D. Isothermal
Answer: B
Rationale: Isobaric processes involve a change in volume at a constant pressure.

6. The Second Law of Thermodynamics implies that:
A. Energy is always conserved
B. Heat can never spontaneously flow from cold to hot
C. Engines can be 100% efficient
D. Perpetual motion machines are possible
Answer: B
Rationale: The Second Law dictates the direction of heat flow and the inevitable increase in
entropy.

7. Angular displacement



for a body starting from rest with constant angular acceleration



after time



is:
A.




B.




C.

,D.




Answer: B
Rationale: Using the rotational kinematic equation



where



.

8. A "Steady State" in thermodynamics means:
A. The system is expanding
B. Parameters like temperature and pressure do not change with time at any point
C. No energy is moving
D. The system is at 0 K
Answer: B
Rationale: While energy may flow through a steady-state system, the properties at any
specific location remain constant.

9. If the net torque on a rotating system is zero:
A. The angular velocity is zero
B. The angular momentum is conserved
C. The moment of inertia is zero
D. The rotational kinetic energy is zero
Answer: B
Rationale: Law of Conservation of Angular Momentum:



if



.

10. In a p-V diagram, an adiabatic curve is:
A. Steeper than an isothermal curve
B. Less steep than an isothermal curve
C. Horizontal
D. Vertical
Answer: A
Rationale: Because



(where

, ) for adiabatic and



for isothermal, the adiabatic gradient is larger.

11. What is the effect of an "Absorption Dynamometer"?
A. It measures the fuel flow
| B. It measures the brake power by absorbing the engine's output
C. It measures the temperature of the exhaust
D. It increases the engine speed
Answer: B
Rationale: It applies a load (torque) to the engine to determine the brake power (



).

12. The "Work Done" during an adiabatic process is equal to:
A. The heat added
B. The negative of the change in internal energy (



)
C. Zero
D. The change in pressure
Answer: B
Rationale: Since



,



, therefore



.

13. The Otto cycle consists of which four processes?
A. 2 Isothermal, 2 Adiabatic
B. 2 Isobaric, 2 Isochoric
C. 2 Adiabatic, 2 Isochoric
D. 2 Isobaric, 2 Isothermal
Answer: C
Rationale: The ideal Otto cycle uses adiabatic compression/expansion and isochoric heat
addition/rejection.

14. A diver pulls their arms in while spinning. Their angular speed increases because:
A. Torque increases