SOLVE JEE (MAIN) 2017 WITH A SMILE – I

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Let Us YOU Solve Physics JEE (MAIN) 2017 Physics Paper

We shall explore more Physics questions from JEE (Main) 2017, Paper-1 in this blog. This exam was held in off-line mode on Sunday, 02 April 2017, at 0930-1230 hours. Students wishing to pursue B.E. /B. Tech courses in Engineering all over India took this exam.

Latecomers to this blog site! Hope you are familiar with our approach by now. We do not solve questions straightaway from the latest Entrance Examination papers. There are a number of websites where you will find such ready-made solutions. In our opinion, such passive give-and-take can hardly boost a student’s confidence. Instead, we trust the abilities of a student who has studied the theories well and is eager to apply them in solving questions/problems.

The large reservoir of video lectures @ PhysicsAcademyOnline.com is an excellent source to learn, relearn or brush up various topics of Physics at advanced school level and introductory college level anywhere in the world. The various competitive examinations, which are held to select a small fraction of examinees for prestigious engineering and medical courses, are an excellent platform to test the question-solving skill. Therefore, in our blogs, we invite students to solve questions on their own from recently held exam papers. It’s a delight to watch them cracking so-called tough questions by quickly connecting them to relevant theories and formulas.

Here we go. JEE (Main) 2017, Paper-1. As usual, it contains 90 questions in total, carrying maximum marks 360, divided equally among Physics, Chemistry and Mathematics. Part-A is Physics, containing 30 MCQs with one correct option. If you choose the correct option, you get 4 marks; if you choose an incorrect option or more than one options (which may include the correct option), you get -1 mark; if you choose none, you get zero. The duration of the exam is three hours; it boils down to one hour for Physics part, that is ideally two minutes for each MCQ.

 

Question 02: A body is thrown vertically upwards. Which one of the following graphs correctly represents its velocity versus time?:

For a body thrown vertically upwards, what is its acceleration through the flight? Hence, what is the kinematic equation that gives its velocity as a function of time?  Subscribe to PhysicsAcademyOnline.com, and watch the lecture: Chapter Name – Mechanics; Category – Basic; Topic Name – Motion in One and Two Dimensions; Video Name – Rectilinear Motion under Gravity.

Which of the given graphs corresponds to the above kinematic equation? For a general study, you may watch: Chapter Name – Mechanics; Category – Basic; Topic Name – Motion in One and Two Dimensions; Video Name – Graphical Analysis of Rectilinear Motion.

However, advancing through the first lecture, you will find the velocity vs time graph itself – plotted with explanation!

 

 

Question 03:  A body of mass m = 10-2 kg is moving in a medium and experiences a frictional force F = – kv2. Its initial speed is v0 = 10 m/s. If, after 10 s, its energy is mv02/8, the value of k will be:

(1) 10-3 kg/m    (2) 10-3 kg/s     (3) 10-4 kg/m     (4) 10-1 kg/m-s

Since the options have different units, you can narrow down the search (if not hitting the correct option straightaway) by dimensional analysis. What is the correct unit of k? Learn the technique from the lecture: Chapter Name – Mechanics; Category – Basic; Topic Name – Physical Quantities and Their Measurement; Video Name – Uses of Dimensional Analysis.

So you cannot avoid numerical calculation! Assuming you remember the formula for kinetic energy, using the condition given, what is the final speed of the body at t = 10 s?

Applying Newton’s second law, what is the equation of motion of the body? How do you express acceleration in derivative form? It’s in the same lecture mentioned earlier:  Chapter Name – Mechanics; Category – Basic; Topic Name – Motion in One and Two Dimensions; Video Name – Graphical Analysis of Rectilinear Motion.

Separate the variables, integrate between limits, and put the data given to evaluate k. Confirmation comes from the video solution below.

 

 

 

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