Physics for Life Sciences Exam Prep – Real Practice Questions, Answers
& Detailed Rationales (Updated 2026) | Mechanics & Motion in
Biological Systems, Energy & Thermodynamics, Waves, Sound & Medical
Imaging Physics, Electricity & Magnetism in Healthcare, Fluid Dynamics &
Blood Flow, Radiation Physics, Scientific Measurement & Life Science
Applications Review
Question 1: Which physical principle best explains how a fish maintains neutral
buoyancy in water?
A. Newton’s second law of motion
B. Archimedes’ principle
C. Pascal’s principle
D. Bernoulli’s equation
CORRECT ANSWER: B. Archimedes’ principle
Rationale: Archimedes’ principle states that the buoyant force on an object submerged
in a fluid is equal to the weight of the fluid displaced by the object. Fish adjust their
buoyancy using swim bladders to displace varying amounts of water, achieving neutral
buoyancy when the buoyant force equals their weight.
Question 2: In the context of human physiology, what does Poiseuille’s law
primarily describe?
A. The diffusion rate of oxygen across alveolar membranes
B. The electrical resistance of neuronal axons
C. The flow rate of a viscous fluid through a cylindrical tube
D. The absorption spectrum of hemoglobin
CORRECT ANSWER: C. The flow rate of a viscous fluid through a cylindrical tube
Rationale: Poiseuille’s law quantifies laminar flow of a Newtonian fluid through a long
cylindrical pipe, showing that flow rate is proportional to the fourth power of the radius
and the pressure gradient, and inversely proportional to fluid viscosity and tube length—
critical for understanding blood flow in vessels.
Question 3: Which of the following best describes the role of Gibbs free energy (ΔG)
in biochemical reactions?
A. It measures the total heat content of a system
B. It determines whether a reaction is spontaneous at constant temperature and
pressure
C. It quantifies the entropy change of the surroundings
D. It defines the activation energy required for enzyme catalysis
CORRECT ANSWER: B. It determines whether a reaction is spontaneous at
constant temperature and pressure
,Rationale: Gibbs free energy combines enthalpy and entropy to predict spontaneity: if
ΔG < 0, the reaction proceeds spontaneously under constant T and P—key for
metabolic pathways like ATP hydrolysis.
Question 4: A red blood cell placed in a hypertonic solution will most likely undergo
which process?
A. Hemolysis
B. Crenation
C. Osmotic equilibrium
D. Active transport
CORRECT ANSWER: B. Crenation
Rationale: In a hypertonic solution, water exits the cell via osmosis due to higher
external solute concentration, causing the cell to shrink and develop a scalloped or
spiky appearance known as crenation.
Question 5: What is the primary physical mechanism by which the human ear
distinguishes different sound frequencies?
A. Amplitude modulation in the auditory nerve
B. Resonance of the tympanic membrane
C. Tonotopic organization of the basilar membrane in the cochlea
D. Doppler shift detection in the semicircular canals
CORRECT ANSWER: C. Tonotopic organization of the basilar membrane in the
cochlea
Rationale: The basilar membrane varies in stiffness along its length; high-frequency
sounds cause maximum vibration near the base, while low frequencies peak near the
apex, enabling frequency discrimination via place coding.
Question 6: Which optical phenomenon is primarily responsible for the focusing of
light onto the retina by the eye’s lens?
A. Diffraction
B. Interference
C. Refraction
D. Scattering
CORRECT ANSWER: C. Refraction
Rationale: Refraction—the bending of light as it passes from one medium to another
with a different refractive index—allows the cornea and lens to converge incoming light
rays onto the retina to form a clear image.
Question 7: In electrocardiography (ECG), what does the QRS complex represent
physiologically?
, A. Atrial repolarization
B. Ventricular depolarization
C. Atrial depolarization
D. Ventricular repolarization
CORRECT ANSWER: B. Ventricular depolarization
Rationale: The QRS complex corresponds to the rapid depolarization of the right and left
ventricles, which initiates ventricular contraction and is the largest deflection on the
ECG due to the greater muscle mass involved.
Question 8: Fick’s first law of diffusion states that the diffusive flux is proportional
to which quantity?
A. The square of the concentration gradient
B. The inverse of molecular weight
C. The negative concentration gradient
D. The temperature gradient
CORRECT ANSWER: C. The negative concentration gradient
Rationale: Fick’s first law asserts that particles diffuse from regions of high to low
concentration, with flux J = –D(∂C/∂x), where D is the diffusion coefficient and the
negative sign indicates movement down the gradient.
Question 9: During walking, the ankle acts as a lever system. What class of lever is
it when the calf muscles lift the body weight?
A. First-class lever
B. Second-class lever
C. Third-class lever
D. Fourth-class lever
CORRECT ANSWER: B. Second-class lever
Rationale: In plantar flexion, the fulcrum is the ball of the foot (metatarsophalangeal
joints), the load is the body weight acting through the tibia, and the effort is applied by
the Achilles tendon posterior to the fulcrum—characteristic of a second-class lever.
Question 10: Why is lead used as shielding in X-ray rooms?
A. It has a low atomic number, minimizing photoelectric absorption
B. It reflects X-rays efficiently due to its metallic luster
C. It has a high atomic number and density, maximizing attenuation of X-rays
D. It emits counter-radiation that cancels incoming X-rays
CORRECT ANSWER: C. It has a high atomic number and density, maximizing
attenuation of X-rays
& Detailed Rationales (Updated 2026) | Mechanics & Motion in
Biological Systems, Energy & Thermodynamics, Waves, Sound & Medical
Imaging Physics, Electricity & Magnetism in Healthcare, Fluid Dynamics &
Blood Flow, Radiation Physics, Scientific Measurement & Life Science
Applications Review
Question 1: Which physical principle best explains how a fish maintains neutral
buoyancy in water?
A. Newton’s second law of motion
B. Archimedes’ principle
C. Pascal’s principle
D. Bernoulli’s equation
CORRECT ANSWER: B. Archimedes’ principle
Rationale: Archimedes’ principle states that the buoyant force on an object submerged
in a fluid is equal to the weight of the fluid displaced by the object. Fish adjust their
buoyancy using swim bladders to displace varying amounts of water, achieving neutral
buoyancy when the buoyant force equals their weight.
Question 2: In the context of human physiology, what does Poiseuille’s law
primarily describe?
A. The diffusion rate of oxygen across alveolar membranes
B. The electrical resistance of neuronal axons
C. The flow rate of a viscous fluid through a cylindrical tube
D. The absorption spectrum of hemoglobin
CORRECT ANSWER: C. The flow rate of a viscous fluid through a cylindrical tube
Rationale: Poiseuille’s law quantifies laminar flow of a Newtonian fluid through a long
cylindrical pipe, showing that flow rate is proportional to the fourth power of the radius
and the pressure gradient, and inversely proportional to fluid viscosity and tube length—
critical for understanding blood flow in vessels.
Question 3: Which of the following best describes the role of Gibbs free energy (ΔG)
in biochemical reactions?
A. It measures the total heat content of a system
B. It determines whether a reaction is spontaneous at constant temperature and
pressure
C. It quantifies the entropy change of the surroundings
D. It defines the activation energy required for enzyme catalysis
CORRECT ANSWER: B. It determines whether a reaction is spontaneous at
constant temperature and pressure
,Rationale: Gibbs free energy combines enthalpy and entropy to predict spontaneity: if
ΔG < 0, the reaction proceeds spontaneously under constant T and P—key for
metabolic pathways like ATP hydrolysis.
Question 4: A red blood cell placed in a hypertonic solution will most likely undergo
which process?
A. Hemolysis
B. Crenation
C. Osmotic equilibrium
D. Active transport
CORRECT ANSWER: B. Crenation
Rationale: In a hypertonic solution, water exits the cell via osmosis due to higher
external solute concentration, causing the cell to shrink and develop a scalloped or
spiky appearance known as crenation.
Question 5: What is the primary physical mechanism by which the human ear
distinguishes different sound frequencies?
A. Amplitude modulation in the auditory nerve
B. Resonance of the tympanic membrane
C. Tonotopic organization of the basilar membrane in the cochlea
D. Doppler shift detection in the semicircular canals
CORRECT ANSWER: C. Tonotopic organization of the basilar membrane in the
cochlea
Rationale: The basilar membrane varies in stiffness along its length; high-frequency
sounds cause maximum vibration near the base, while low frequencies peak near the
apex, enabling frequency discrimination via place coding.
Question 6: Which optical phenomenon is primarily responsible for the focusing of
light onto the retina by the eye’s lens?
A. Diffraction
B. Interference
C. Refraction
D. Scattering
CORRECT ANSWER: C. Refraction
Rationale: Refraction—the bending of light as it passes from one medium to another
with a different refractive index—allows the cornea and lens to converge incoming light
rays onto the retina to form a clear image.
Question 7: In electrocardiography (ECG), what does the QRS complex represent
physiologically?
, A. Atrial repolarization
B. Ventricular depolarization
C. Atrial depolarization
D. Ventricular repolarization
CORRECT ANSWER: B. Ventricular depolarization
Rationale: The QRS complex corresponds to the rapid depolarization of the right and left
ventricles, which initiates ventricular contraction and is the largest deflection on the
ECG due to the greater muscle mass involved.
Question 8: Fick’s first law of diffusion states that the diffusive flux is proportional
to which quantity?
A. The square of the concentration gradient
B. The inverse of molecular weight
C. The negative concentration gradient
D. The temperature gradient
CORRECT ANSWER: C. The negative concentration gradient
Rationale: Fick’s first law asserts that particles diffuse from regions of high to low
concentration, with flux J = –D(∂C/∂x), where D is the diffusion coefficient and the
negative sign indicates movement down the gradient.
Question 9: During walking, the ankle acts as a lever system. What class of lever is
it when the calf muscles lift the body weight?
A. First-class lever
B. Second-class lever
C. Third-class lever
D. Fourth-class lever
CORRECT ANSWER: B. Second-class lever
Rationale: In plantar flexion, the fulcrum is the ball of the foot (metatarsophalangeal
joints), the load is the body weight acting through the tibia, and the effort is applied by
the Achilles tendon posterior to the fulcrum—characteristic of a second-class lever.
Question 10: Why is lead used as shielding in X-ray rooms?
A. It has a low atomic number, minimizing photoelectric absorption
B. It reflects X-rays efficiently due to its metallic luster
C. It has a high atomic number and density, maximizing attenuation of X-rays
D. It emits counter-radiation that cancels incoming X-rays
CORRECT ANSWER: C. It has a high atomic number and density, maximizing
attenuation of X-rays
