JEE-Main-26-08-2021-Shift-1 (Memory Based)
Exam Overview
The Joint Entrance Examination (JEE) Main is one of the most competitive engineering entrance exams in India conducted by the National Testing Agency (NTA). The August 26, 2021 Shift 1 examination was part of the multiple sessions held that year due to the COVID-19 pandemic situation.
This page provides a comprehensive analysis and memory-based questions from JEE-Main held on August 26, 2021, during the first shift. This analysis is based on student reactions and memory-based questions collected after the examination.
Exam Pattern and Structure
The JEE-Main examination follows a standardized pattern across all sessions:
- Total duration: 3 hours
- Total questions: 90 questions (30 from each subject)
- Maximum marks: 300 marks
- Subjects: Physics, Chemistry, and Mathematics
- Question types: Multiple Choice Questions (MCQ) and Numerical Value based questions
- Marking scheme: +4 for correct answer, -1 for incorrect in MCQs; +4 for correct, 0 for incorrect in numerical questions
Overall Difficulty Level
According to student reactions and expert analysis, the difficulty level of JEE-Main conducted on August 26, 2021 (Shift 1) can be summarized as follows:
- Moderate Overall
- Moderate Physics
- Easy to Moderate Chemistry
- Moderate Mathematics
Subject-wise Analysis
Physics
Physics section was considered moderate with a balanced mix of concepts from different areas. Many questions were formula-based, while some required deeper conceptual understanding. The section included questions from Mechanics, Electrodynamics, Thermodynamics, Optics, and Modern Physics.
Memory-based Question 1 (Physics):
A particle moves in a straight line with initial velocity u and constant acceleration a. The displacement in the nth second is:
This formula directly gives the displacement in the nth second for a particle with initial velocity u and acceleration a.
Memory-based Question 2 (Physics):
Two identical charges q are placed at a distance d apart. If a third identical charge q is placed at the midpoint of the line joining them, what is the net force on this third charge?
Chemistry
The Chemistry section was regarded as relatively easy to moderate compared to previous shifts. Both organic and inorganic chemistry had almost equal weightage, with numerical-based questions being more from physical chemistry. Questions from environmental chemistry, coordination compounds, and biomolecules were prominent.
Memory-based Question 1 (Chemistry):
Which of the following is used as a catalyst in the Ostwald process?
- A) Platinum
- B) Nickel
- C) Iron
- D) Copper
The Ostwald process is used for the industrial production of nitric acid, and platinum is used as a catalyst in this process along with rhodium.
Memory-based Question 2 (Chemistry):
The correct order of acidic strength for the following compounds is: OH | I: C6H5-COOH II: C6H5-OH III: CH3-COOH IV: C6H5-CH2-COOH
Benzene ring increases the acidity of carboxylic acid due to resonance stabilization of the anion. Phenol is less acidic compared to carboxylic acids.
Mathematics
Mathematics section was moderate with questions from algebra, calculus, coordinate geometry, and vectors being prominent. Some questions were lengthy and calculation-intensive, requiring a good command over concepts and formulas. Vector algebra and 3D geometry had significant weightage.
Memory-based Question 1 (Mathematics):
If y = x(x-3), find the point of local maxima and local minima.
For critical points, dy/dx = 0, which gives x = 1 and x = 3.
Using the second derivative test: dy/dx = 6x - 12
At x = 1: dy/dx = 6(1) - 12 = -6 < 0 (local maxima)
At x = 3: dy/dx = 6(3) - 12 = 6 > 0 (local minima)
Therefore, local maxima occurs at x = 1 with y = 4, and local minima occurs at x = 3 with y = 0.
Memory-based Question 2 (Mathematics):
Find the equation of the plane passing through the point (2, 3, 1) and perpendicular to the line of intersection of the planes x + 2y + 3z = 4 and 2x + y - z = -5.
Normal vectors: n = (1, 2, 3) and n = (2, 1, -1)
Direction ratios = n n = (2(-1) - 3(1), 3(2) - 1(-1), 1(1) - 2(2))
= (-2 - 3, 6 + 1, 1 - 4) = (-5, 7, -3)
Since the required plane is perpendicular to the line of intersection, the direction ratios of the line will be the normal to the plane.
Therefore, the equation of the plane is: -5(x - 2) + 7(y - 3) - 3(z - 1) = 0
or: -5x + 10 + 7y - 21 - 3z + 3 = 0
or: 5x - 7y + 3z + 8 = 0
Topic-wise Distribution
The approximate distribution of questions across different topics is given below:
Physics Topic Distribution
| Topic | Number of Questions |
|---|---|
| Mechanics | 8-10 |
| Electrodynamics | 7-9 |
| Thermodynamics | 3-4 |
| Optics | 3-4 |
| Modern Physics | 4-5 |
| Others | 3-4 |
Chemistry Topic Distribution
| Topic | Number of Questions |
|---|---|
| Physical Chemistry | 10-12 |
| Organic Chemistry | 9-10 |
| Inorganic Chemistry | 8-10 |
Mathematics Topic Distribution
| Topic | Number of Questions |
|---|---|
| Algebra | 9-10 |
| Calculus | 8-9 |
| Coordinate Geometry | 5-6 |
| Vector Algebra | 3-4 |
| 3D Geometry | 2-3 |
| Trigonometry | 2-3 |
Expert Review and Expected Cutoff
Based on the analysis of the JEE-Main August 26, 2021 (Shift 1) paper:
- Physics had a good balance between conceptual and calculation-based questions
- Chemistry was relatively easier compared to other shifts with more direct questions
- Mathematics required quick calculation skills and strong conceptual understanding
The expected score range for different percentiles are approximately:
- 100-150 marks could place a student in the 90-95 percentile range
- 150-200 marks could place a student in the 95-98 percentile range
- Above 200 marks could place a student in the 98-99+ percentile range
Conclusion
The JEE-Main 26th August 2021 Shift 1 paper was of moderate difficulty, with Chemistry being relatively easier compared to Physics and Mathematics. A student who had prepared well and had a good understanding of concepts across all subjects would have been able to attempt a good number of questions.
It is crucial for aspirants to analyze the question papers of different shifts to understand the pattern and difficulty level. This analysis can help in strategizing preparation for future attempts.
Note: The analysis and memory-based questions provided here are based on student recollections and may not be 100% accurate. Students are advised to refer to official sources for complete information.
JEE-Main-26-08-2021-Shift-1 (Memory Based) and Reference File Download Link
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