Why Physics Appears on the HESI A2
Not every nursing program requires the Physics section of the HESI A2, but for those that do, it typically contains 25 questions covering fundamental concepts in mechanics, energy, waves, electricity, and thermodynamics. Physics principles underpin many clinical concepts — from understanding blood pressure (fluid dynamics) to operating imaging equipment (electromagnetic waves) and defibrillator use (electrical current).
These practice questions focus on the most commonly tested physics concepts and include step-by-step solutions to help you master the problem-solving approach the HESI A2 expects.
Part 1: Forces & Motion — Newton's Laws (Questions 1–6)
Question 1
A 5 kg box is pushed across a frictionless surface with a force of 20 N. What is the acceleration of the box?
- A) 2 m/s²
- B) 4 m/s²
- C) 10 m/s²
- D) 100 m/s²
Answer: B
Explanation: Using Newton's Second Law: F = ma, so a = F/m = 20 N ÷ 5 kg = 4 m/s². Force is measured in Newtons (N), where 1 N = 1 kg·m/s². This formula is one of the most frequently tested physics concepts on the HESI A2.
Question 2
According to Newton's Third Law, when a nurse pushes a wheelchair forward, what happens?
- A) The wheelchair pushes back on the nurse with an equal and opposite force.
- B) The wheelchair accelerates without any reaction force.
- C) The nurse experiences no force from the wheelchair.
- D) The wheelchair pushes forward on the nurse with an equal force.
Answer: A
Explanation: Newton's Third Law states that for every action, there is an equal and opposite reaction. When the nurse exerts a forward force on the wheelchair, the wheelchair exerts an equal force backward on the nurse. These action-reaction forces act on different objects, which is why both can still move forward (due to friction with the ground).
Question 3
A patient weighing 80 kg is lying on a hospital bed. What is the gravitational force (weight) acting on the patient? (Use g = 9.8 m/s²)
- A) 80 N
- B) 784 N
- C) 8.16 N
- D) 7,840 N
Answer: B
Explanation: Weight = mass × gravity = 80 kg × 9.8 m/s² = 784 N. Weight is a force measured in Newtons, not kilograms. Mass (kg) measures the amount of matter in an object and remains constant; weight (N) depends on gravitational acceleration and changes with location (e.g., less on the Moon).
Question 4
An object is moving at a constant velocity in a straight line. What can be said about the net force on this object?
- A) The net force is in the direction of motion.
- B) The net force is zero.
- C) The net force is increasing.
- D) The net force equals the object's weight.
Answer: B
Explanation: Newton's First Law (Law of Inertia) states that an object in motion stays in motion at constant velocity unless acted upon by an unbalanced force. If velocity is constant (no acceleration), then by F = ma, the net force must be zero. This means all forces acting on the object are balanced.
Question 5
A 1,200 kg car accelerates from 0 to 20 m/s in 10 seconds. What is the net force acting on the car?
- A) 120 N
- B) 2,400 N
- C) 12,000 N
- D) 24,000 N
Answer: B
Explanation: First, find acceleration: a = Δv/Δt = (20 - 0)/10 = 2 m/s². Then apply Newton's Second Law: F = ma = 1,200 kg × 2 m/s² = 2,400 N. This two-step process — finding acceleration first, then calculating force — is a common HESI A2 problem pattern.
Question 6
What is the coefficient of friction if a 50 N force is needed to move a 200 N block at constant speed across a surface?
- A) 0.10
- B) 0.25
- C) 0.50
- D) 4.00
Answer: B
Explanation: The coefficient of friction (μ) = friction force ÷ normal force = 50 N ÷ 200 N = 0.25. At constant speed, the applied force equals the friction force (net force is zero). The normal force on a flat surface equals the weight of the object. Friction is clinically relevant — it affects patient transfers and wheelchair movement.
Part 2: Energy, Work & Power (Questions 7–12)
Question 7
How much work is done when a nurse lifts a 10 kg supply box 1.5 meters onto a shelf? (Use g = 9.8 m/s²)
- A) 15 J
- B) 98 J
- C) 147 J
- D) 150 J
Answer: C
Explanation: Work = Force × Distance. The force needed to lift the box equals its weight: F = mg = 10 × 9.8 = 98 N. Work = 98 N × 1.5 m = 147 J (Joules). Work is measured in Joules, where 1 J = 1 N·m. Note that the force must be in the direction of displacement.
Question 8
A ball is thrown upward. At the highest point of its trajectory, which of the following is true?
- A) Both kinetic and potential energy are at maximum.
- B) Kinetic energy is at maximum, potential energy is at minimum.
- C) Kinetic energy is zero, potential energy is at maximum.
- D) Both kinetic and potential energy are zero.
Answer: C
Explanation: At the highest point, the ball momentarily stops (velocity = 0), so kinetic energy (KE = ½mv²) is zero. All the kinetic energy has been converted to gravitational potential energy (PE = mgh), which is at its maximum because height is maximum. This illustrates the conservation of mechanical energy.
Question 9
What is the kinetic energy of a 2 kg object moving at 3 m/s?
- A) 3 J
- B) 6 J
- C) 9 J
- D) 18 J
Answer: C
Explanation: Kinetic energy = ½mv² = ½ × 2 kg × (3 m/s)² = ½ × 2 × 9 = 9 J. Notice that velocity is squared — this means doubling the speed quadruples the kinetic energy. This concept explains why high-speed collisions are exponentially more dangerous than low-speed ones.
Question 10
A machine does 500 J of work in 10 seconds. What is its power output?
- A) 5 W
- B) 50 W
- C) 500 W
- D) 5,000 W
Answer: B
Explanation: Power = Work ÷ Time = 500 J ÷ 10 s = 50 W (Watts). Power measures the rate at which work is done or energy is transferred. 1 Watt = 1 Joule per second. This concept applies to medical equipment — a defibrillator, for instance, delivers a specific amount of energy (Joules) in a very short time, requiring high power.
Question 11
If a simple machine has a mechanical advantage of 4, how much input force is needed to lift a 200 N load?
- A) 50 N
- B) 100 N
- C) 200 N
- D) 800 N
Answer: A
Explanation: Mechanical Advantage (MA) = Output Force ÷ Input Force. So Input Force = Output Force ÷ MA = 200 N ÷ 4 = 50 N. Simple machines like levers, pulleys, and ramps multiply force — a patient lift (Hoyer lift) uses mechanical advantage to help nurses move patients safely with less physical effort.
Question 12
According to the law of conservation of energy, what happens to the total energy in a closed system?
- A) It increases over time.
- B) It decreases due to friction.
- C) It remains constant but can change forms.
- D) It is destroyed when work is done.
Answer: C
Explanation: The law of conservation of energy states that energy cannot be created or destroyed — only transformed from one form to another. In a closed system, total energy remains constant. For example, when a ball drops, potential energy converts to kinetic energy. Even friction converts kinetic energy to thermal energy — the total energy is conserved.
Part 3: Waves & Sound (Questions 13–17)
Question 13
A wave has a frequency of 500 Hz and a wavelength of 0.6 m. What is the wave's speed?
- A) 30 m/s
- B) 300 m/s
- C) 833 m/s
- D) 3,000 m/s
Answer: B
Explanation: Wave speed = frequency × wavelength = 500 Hz × 0.6 m = 300 m/s. This is the universal wave equation (v = fλ) that applies to all types of waves — sound, light, and water waves. Hz (Hertz) means cycles per second.
Question 14
Which type of wave requires a medium to travel through?
- A) Electromagnetic waves
- B) Light waves
- C) Sound waves
- D) Radio waves
Answer: C
Explanation: Sound waves are mechanical waves that require a medium (solid, liquid, or gas) to propagate. They cannot travel through a vacuum. Electromagnetic waves (light, radio, X-rays) do not require a medium and can travel through space. This is why ultrasound requires gel — the gel serves as a medium for sound wave transmission between the transducer and the body.
Question 15
What happens to the pitch of a sound wave when its frequency increases?
- A) The pitch decreases.
- B) The pitch stays the same.
- C) The pitch increases.
- D) The pitch becomes inaudible.
Answer: C
Explanation: Pitch is directly related to frequency — higher frequency means higher pitch, and lower frequency means lower pitch. Amplitude, not frequency, determines loudness (volume). In clinical settings, different stethoscope sides (bell vs. diaphragm) are designed to detect low-frequency vs. high-frequency body sounds.
Question 16
An ambulance siren sounds higher-pitched as it approaches and lower-pitched as it moves away. This phenomenon is called:
- A) Resonance
- B) Refraction
- C) Diffraction
- D) The Doppler effect
Answer: D
Explanation: The Doppler effect describes the change in observed frequency (and thus pitch) of a wave when the source and observer are in relative motion. As the ambulance approaches, sound waves are compressed (higher frequency/pitch); as it recedes, waves are stretched (lower frequency/pitch). Doppler ultrasound uses this same principle to measure blood flow velocity.
Question 17
Which of the following correctly lists electromagnetic waves from lowest to highest frequency?
- A) Gamma rays, X-rays, visible light, radio waves
- B) Radio waves, microwaves, visible light, X-rays
- C) X-rays, ultraviolet, infrared, radio waves
- D) Visible light, infrared, microwaves, gamma rays
Answer: B
Explanation: The electromagnetic spectrum from lowest to highest frequency is: radio waves → microwaves → infrared → visible light → ultraviolet → X-rays → gamma rays. Higher frequency means higher energy and shorter wavelength. In healthcare, X-rays and gamma rays are high-energy radiation used in imaging and cancer treatment, while infrared is used in thermal imaging.
Part 4: Electricity & Circuits (Questions 18–22)
Question 18
What is the current flowing through a circuit with a voltage of 12 V and a resistance of 4 Ω?
- A) 0.33 A
- B) 3 A
- C) 16 A
- D) 48 A
Answer: B
Explanation: Using Ohm's Law: V = IR, so I = V/R = 12 V ÷ 4 Ω = 3 A (Amperes). Ohm's Law is the most important electrical formula on the HESI A2. Voltage (V) is the "push" driving current, current (I) is the flow of charge, and resistance (R) opposes current flow.
Question 19
In a series circuit with three resistors of 2 Ω, 3 Ω, and 5 Ω, what is the total resistance?
- A) 0.97 Ω
- B) 3.33 Ω
- C) 10 Ω
- D) 30 Ω
Answer: C
Explanation: In a series circuit, total resistance is the sum of individual resistances: R_total = R₁ + R₂ + R₃ = 2 + 3 + 5 = 10 Ω. In series circuits, current is the same through each component, but voltage divides among them. (In parallel circuits, the calculation uses reciprocals: 1/R_total = 1/R₁ + 1/R₂ + 1/R₃.)
Question 20
What happens to the current in a circuit if the resistance is doubled while voltage remains constant?
- A) Current doubles.
- B) Current is halved.
- C) Current stays the same.
- D) Current quadruples.
Answer: B
Explanation: From Ohm's Law (I = V/R), current is inversely proportional to resistance when voltage is constant. If R doubles, I is halved. This principle is clinically relevant — electrical safety guidelines exist because even small currents through the body (as low as 0.1 A through the heart) can be fatal.
Question 21
How much electrical power is consumed by a device with a current of 5 A and a voltage of 120 V?
- A) 24 W
- B) 25 W
- C) 600 W
- D) 6,000 W
Answer: C
Explanation: Electrical power = voltage × current: P = VI = 120 V × 5 A = 600 W. Power is measured in Watts. Hospital equipment ratings are given in Watts to prevent overloading circuits. You can also calculate power using P = I²R or P = V²/R by substituting Ohm's Law.
Question 22
Which of the following materials is the best conductor of electricity?
- A) Rubber
- B) Glass
- C) Copper
- D) Plastic
Answer: C
Explanation: Conductors are materials that allow electric current to flow easily because they have free-moving electrons. Metals — especially copper, silver, and aluminum — are excellent conductors. Rubber, glass, and plastic are insulators that resist current flow. In healthcare, this is why electrical wires use copper cores with rubber/plastic insulation for safety.
Part 5: Thermodynamics & Fluid Basics (Questions 23–25)
Question 23
How much heat energy is needed to raise the temperature of 2 kg of water by 5°C? (Specific heat of water = 4,186 J/kg·°C)
- A) 4,186 J
- B) 20,930 J
- C) 41,860 J
- D) 209,300 J
Answer: C
Explanation: Using Q = mcΔT: Q = 2 kg × 4,186 J/kg·°C × 5°C = 41,860 J. The specific heat capacity of water is exceptionally high, meaning water absorbs a large amount of energy before its temperature changes significantly. This is why the human body (which is ~60% water) maintains a relatively stable temperature.
Question 24
Heat transfers from a warm coffee mug to your hand primarily by which method?
- A) Radiation
- B) Convection
- C) Conduction
- D) Insulation
Answer: C
Explanation: Conduction is heat transfer through direct physical contact between objects. When you hold a warm mug, thermal energy flows from the hotter object (mug) to the cooler object (hand) through molecular collisions. Convection transfers heat through fluid movement (e.g., warm air rising). Radiation transfers heat through electromagnetic waves (e.g., the sun warming your face). Insulation is not a method of heat transfer but rather slows it.
Question 25
What is the pressure at the bottom of a column of water 2 meters deep? (Density of water = 1,000 kg/m³, g = 9.8 m/s²)
- A) 1,960 Pa
- B) 9,800 Pa
- C) 19,600 Pa
- D) 98,000 Pa
Answer: C
Explanation: Fluid pressure = density × gravity × height: P = ρgh = 1,000 kg/m³ × 9.8 m/s² × 2 m = 19,600 Pa (Pascals). Pressure increases with depth, which is the principle behind blood pressure measurement — the pressure exerted by blood against vessel walls depends on the volume and characteristics of the fluid column.
Essential Physics Formulas for the HESI A2
Keep these key formulas ready for exam day:
Mechanics: F = ma (Newton's Second Law) • W = Fd (Work) • KE = ½mv² (Kinetic Energy) • PE = mgh (Potential Energy) • P = W/t (Power) • Weight = mg
Waves: v = fλ (Wave Speed) • Speed of light = 3 × 10⁸ m/s • Speed of sound in air ≈ 343 m/s
Electricity: V = IR (Ohm's Law) • P = VI (Electrical Power) • Series: R_total = R₁ + R₂ + R₃ • Parallel: 1/R_total = 1/R₁ + 1/R₂ + 1/R₃
Thermodynamics: Q = mcΔT (Heat Energy) • P = ρgh (Fluid Pressure)
How to Study Physics for the HESI A2
Focus on concepts over calculations. The HESI A2 physics section tests your understanding of fundamental principles more than your ability to do complex math. Know what each formula means and when to apply it.
Master unit analysis. Always check that your units cancel correctly. If a question asks for Newtons, your answer must have units of kg·m/s². Unit analysis can help you determine the correct formula even if you can't remember it.
Connect physics to nursing. Understanding why blood pressure depends on fluid dynamics, why defibrillators deliver energy in Joules, or how ultrasound uses wave properties will make physics concepts more intuitive and easier to remember on test day.
Practice the two-step problems. Many HESI A2 physics questions require you to calculate one value (like acceleration) and then use it to find another (like force). Practice recognizing when a problem requires multiple steps.
Don't skip the fundamentals. Newton's three laws, conservation of energy, Ohm's Law, and the wave equation account for the majority of physics questions. Master these before moving to more advanced topics.