What fraction of a radioactive sample remains undecayed after three half-lives?
Correct answer C. 1/8
Subject / 480 questions
MDCAT ECAT Physics MCQs
MDCAT ECAT Physics MCQs are multiple-choice questions covering the full FSc physics syllabus set for medical and engineering entry tests, from vectors and motion to electricity, modern physics and nuclear physics. Each unit is practised separately, and every question on MCQs360 shows its correct answer instantly.
- Electromagnetic Induction 30
- Fluid Dynamics 30
- Electrostatics 30
- Electronics 30
- Electromagnetism 30
- Current Electricity 30
- Work and Energy 30
- Waves 30
- Vectors and Equilibrium 30
- Nuclear Physics 30
- Dawn of Modern Physics 30
- Thermodynamics 30
- Rotational and Circular Motion 30
- Atomic Spectra 30
- Alternating Current 30
- Force and Motion 30
A 64 g sample of a radioisotope has a half-life of 2 hours. What mass of the isotope remains undecayed after 8 hours?
Correct answer C. 4 g
The activity of a source falls from 800 Bq to 100 Bq. If its half-life is 6 hours, how long did this take?
Correct answer C. 18 hours
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A radioisotope has a decay constant of 0.0231 per day. What is its half-life (T½ = 0.693/λ)?
Correct answer D. 30 days
Radium-226 (²²⁶₈₈Ra) decays by emitting one alpha particle. What are the mass number and atomic number of the daughter nucleus?
Correct answer D. A = 222, Z = 86
Uranium-238 (²³⁸₉₂U) decays through a series to stable lead-206 (²⁰⁶₈₂Pb). How many alpha and beta-minus particles are emitted in total?
Correct answer C. 8 alpha and 6 beta
What percentage of a radioactive sample has decayed after two half-lives?
Correct answer D. 75%
A sample contains 2.0 × 10²⁰ radioactive nuclei with decay constant 1.5 × 10⁻¹⁰ s⁻¹. What is its activity?
Correct answer C. 3.0 × 10¹⁰ Bq
Technetium-99m has a half-life of 6 hours. What percentage of an injected dose remains after 24 hours?
Correct answer D. 6.25%
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Three-quarters of a radioactive sample decays in 10 minutes. What is its half-life?
Correct answer B. 5 minutes
When a nucleus undergoes beta-minus decay, what happens to its mass number and atomic number?
Correct answer C. A stays the same and Z increases by 1
The half-life of a radioactive isotope is the time taken for ____
Correct answer D. half of its undecayed nuclei to decay
The decay constant λ of a radioactive isotope represents ____
Correct answer C. the probability per unit time that a nucleus will decay
One becquerel (Bq) is equal to ____
Correct answer A. one decay per second
Which radioisotope is widely used as a source of gamma rays for cancer radiotherapy?
Correct answer B. Cobalt-60
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Why are radioactive tracers used in medical diagnosis usually chosen to have short half-lives?
Correct answer C. So that the patient receives a small total radiation dose
What is the SI unit of equivalent (biological) radiation dose?
Correct answer D. Sievert
How does ionising radiation mainly cause biological damage to living cells?
Correct answer B. By ionising molecules such as DNA, which can kill cells or cause mutations
How many neutrons are present in a nucleus of ²³⁸₉₂U?
Correct answer B. 146
A radioactive isotope has a half-life of 1386 s. What is its decay constant (λ = 0.693/T½)?
Correct answer C. 5.0 × 10⁻⁴ s⁻¹
About MDCAT ECAT Physics MCQs
This subject follows the units of the PMDC uniform MDCAT curriculum. Mechanics comes first: Vectors and Equilibrium, Force and Motion, Work and Energy, Rotational and Circular Motion and Fluid Dynamics. Waves and Thermodynamics follow, then the electricity block of Electrostatics, Current Electricity, Electromagnetism, Electromagnetic Induction, Alternating Current and Electronics. The paper ends with modern physics: Dawn of Modern Physics, Atomic Spectra and Nuclear Physics. In the PMDC MDCAT paper of 180 MCQs, Physics carries 36 questions, a fifth of the total, and there is no negative marking. Questions mix definitions, laws and short calculations with standard constants, so practise both the concepts and quick numerical work. The same units serve ECAT, NUMS and FSc board preparation.
Key facts to remember
- Physics has 36 of the 180 MCQs in the PMDC uniform MDCAT paper, which has no negative marking.
- Newton's second law states that force equals the rate of change of momentum: F = Δp/Δt.
- Coulomb's law gives the force between point charges as F = kq₁q₂/r², with k ≈ 9 × 10⁹ N m² C⁻².
- The energy of a photon is E = hf, where h = 6.63 × 10⁻³⁴ J s is Planck's constant.
- The decay constant and half-life of a radioisotope are related by λ = 0.693/T½.
Exams that include MDCAT ECAT Physics MCQs
Pakistan
- MDCAT
- ECAT (UET)
- NUMS
- AKU
- FSc boards
India
- NEET
- JEE Main
Bangladesh
- HSC
- Medical Admission Test
How to prepare for MDCAT ECAT Physics MCQs
- Work through the units in syllabus order, finishing each unit's MCQs before moving on, so later topics such as induction build on earlier ones.
- Keep a one-page formula sheet per unit and practise rearranging each formula, as many MCQs are one-step calculations.
- Learn the standard constants (g, e, h, c, k) to two significant figures to speed up numerical questions.
- Since there is no negative marking in MDCAT, answer every question, then revisit the ones you got wrong a few days later.
Frequently asked questions
How many Physics MCQs are in the MDCAT paper?
Under the PMDC uniform MDCAT curriculum, Physics has 36 MCQs out of a total of 180, and the paper is three hours long with no negative marking. Biology and Chemistry carry more questions, so Physics rewards accurate, quick working.
Which exams use MDCAT ECAT Physics MCQs?
These MCQs suit MDCAT, ECAT (UET), NUMS and AKU entry tests in Pakistan and FSc board exams. The same physics is tested in NEET and JEE Main in India and in HSC and the medical admission test in Bangladesh.
Which physics units should I revise first for MDCAT?
Start with mechanics (vectors, motion, work and energy), since its ideas recur in later units. Then cover electrostatics, current electricity and magnetism together, and finish with modern and nuclear physics, which are short units with many direct, fact-based questions.
Last reviewed October 2026