You don't need to be get tensed. If you want to crack this exam you need to be self motivated and determined. You can first focus on the chapters which have more weight-age in the exam. You can also go through past year problems to know about the paper pattern and level of questions. Try to solve mock test papers to know your strength and weakness and to know where you stand among other competitors. You can also use below tool to know about the important topics for your preparation. You can check your preparation level and where you stand with recommendations and improvement plan. Click on the below link- www.engineering.careers360.com/prepmeter/jee-main?icn=jeemain-cp&ici=forum

Below is the syllabus of JEE Main-

Mathematics

Sets, Relations & Functions, Complex Numbers & Quadratic Equations, Matrices & Determinants, Permutations & Combinations, Binomial Theorem, Mathematical Induction, Limit, Continuity & Differentiability, Sequences & Series, Differential Equations, Integral Calculus, Three Dimensional Geometry, Co-ordinate Geometry, Statistics & Probability, Vector Algebra, Mathematical Reasoning and Trigonometry.

Physics:

Physics & Measurement, Laws of Motion, Kinematics, Work, Energy & Power, Gravitation, Rotational Motion, Properties of Solids & Liquids, Kinetic Theory of Gases, Thermodynamics, Electrostatics, Oscillations & Waves, Magnetic Effects of Current & Magnetism, Current Electricity, Electromagnetic Induction & Alternating Currents, Optics, Electromagnetic Waves, Dual Nature of Matter & Radiation, Electronic Devices, Atoms & Nuclei, Communication Systems, etc.

Chemistry:

Physical Chemistry: Some Basic concepts in Chemistry, Atomic Structure, States of Matter, Chemical Bonding & Molecular Structure, Solutions, Chemical Thermodynamics, Redox Reactions & Electrochemistry, Equilibrium, Chemical Kinetics, Surface Chemistry, etc.

Inorganic Chemistry: General Principles & Process of Isolation of Metals, Hydrogen, Classification of Elements & Periodicity in Properties, p – Block Elements, s – Block Element, Co-ordination Compounds, d – and f – Block Elements, Environmental Chemistry, etc.

Organic Chemistry: Some Basic Principles of Organic Chemistry, Purification & Characterisation of Organic Compounds, Organic Compounds Containing Halogens, Hydrocarbons, Organic Compounds Containing Oxygen, Polymers, Organic Compounds Containing Nitrogen, Bio Molecules, Principles Related to Practical Chemistry, Chemistry in Everyday Life, etc.

To analyse your preparation level you can use below tool-

Click on the below link-

www.engineering.careers360.com/prepmeter/jee-main?icn=jeemain-cp&ici=forum  

No. Overall marks will be count to prepare merit list. there is no subject wise cut off for DTU or JEE Main.

Qualifying marks criteria for B. E./B. Tech at DTU :

-Candidates need to have secured at least 60% aggregate marks in Physics, Chemistry and Mathematics at Senior School Certificate Examination Level/XII.
-They also need to have passed English as a subject (Core or Elective) at Senior School Certificate Examination Level


You did not mention your category so i am assuming General category.

To get Mechanical branch under Delhi home state quota and general category, your rank should be under 15000 in JEE Main and marks should be between 170-80 marks.

You can check category and branch wise cut off of DTU, Delhi by below link:

DTU Cut Off

Good Luck.

Yes, it varies branch to branch.