JEE MAIN 2020 NEWS

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Kinematics is the field of mechanics that describes the motion of points, objects, or systems. The weightage of Kinematics in JEE Main is around 3 to 4% and candidates can also expect direct questions from this section which makes it one of the scoring topics. To help candidates in their preparation we are providing the revision notes of Kinematics that consist of all the important concepts, formulas, and facts. **Check JEE Main Physics Syllabus**

- Knowledge of formulas, dimensions, graphs is a must to score in this section and these notes will help you in retaining the maximum facts and formulae.
- Some of the important sub-topics from where candidates can expect at least 1 question are Speed, Distance, Velocity, Motion in a Straight Line, Acceleration.

We have also added some quick notes with all the important information so that you can quickly go through the entire topic. Other than that you can also get the sample questions along with tips and tricks to solve those questions.

**Must Read:**

The frame of reference is a set of axes that is used to specify or mention the position of the object in the space. The coordinate system has a set of the rectangular axes that consists of three mutually perpendicular axes X, Y, Z. The point at which these three axes intersect each other is called Origin or Reference Point.

Distance and Displacement are one of the major topics in Kinematics. Candidates must have a clear understanding of the basics of these two terms. With the help of this comparison table, you can easily remember and revise these two topics.

Terms | Distance | Displacement |
---|---|---|

Definition | It is known as Path Length | It is the difference between final & initial position |

Quantity | Scalar | Vector |

Relation with Time | Never reduces time | Displacement of an object changes with time |

Result | Distance covered can never be Negative | Displacement of an object can be Negative, Positive or Zero |

Units | SI unit is meter; m | SI unit is meter; m |

Dimension | M^{0}L^{0}T^{1} | M^{0}L^{0}T^{1} |

Distance/Displacement Time Graph | Represents the Speed of Object | Represents Velocity |

**Question: An object moves 6 m north, 8 m east, and 10m vertically upwards. Calculate the resultant displacement from the initial position?**

- 10√2m
- 10m
- 10√2m
- 10×2m

**Solution: (1)**

**Question: A person moves 30 m north and then 20 m towards the east and finally 30√2m in south-west direction. What will be the displacement of the person from the origin?**

- 10 m along north
- 10 m long south
- 10 m along west
- Zero

**Solution: (3)**

**Read How to Effectively Prepare for the Coming JEE Main Session from Home?**

Similarly, we have prepared a comparison table for Speed and Velocity. The table includes all the important information related to speed and velocity.

Terms | Speed | Velocity |
---|---|---|

Definition | It is the ratio of distance traveled by the time to the time taken | It is the ratio of displacement to the total time taken by the object |

Formula | Speed = Distance Travelled/ Time Taken | Velocity = Displacement/ Total Time |

Quantity | Scalar | Vector |

Units | SI units m/s | SI units m/s |

Dimension | M^{0}LT^{-1} | M^{0}LT^{-1} |

Result | Speed of an Object can never be Negative | Speed of an object can be Negative, Positive or Zero |

Types of Speed and Velocity | ||

Uniform | If an object covers equal distance in equal intervals of time | |

Non Uniform | If an object covers equal distance in an unequal time interval or vice-versa | |

Average | The ratio of total path length divided by the total time duration | |

Instantaneous | Speed/ Velocity of the body at any instant of time. |

**Question: The acceleration versus time of the particle is as provided in the figure and the particle starts from rest. What will be the maximum speed of the particle?**

- 110 m/s
- 55 m/s
- 550 m/s
- 660 m/s

**Solution: (2)**

**Question: A man throws balls with the same speed vertically upwards one after the other at an interval of 2 seconds. Calculate the speed of the throw so that more than two balls are in the sky at any time? Also Given that g=9.8m/s2**

- At least 0.8 m/s
- Any speed less than 19.6 m/s
- Only with speed 19.6 m/s
- More than 19.6 m/s

**Solution: (4)**

- Before understanding the concept of Motion of Straight Line we need to understand that what is Position and Motion.
- The position of an object is very important to describe the motion of that object. The position of the object is the set of the axes from the reference point.
- For Example, if we consider the above image then the position of point A from the point O i.e. a reference point can be defined as,

**Motion: **The object or body is said to be in motion if it changes its position with time and with respect to its surroundings. The representation of the motion of an object can be done with the help of a position-time graph.

When an object moves along the straight line and covers the equal distance in an equal interval of time then the motion is known as uniform motion.

When an object covers equal distance in unequal time or unequal distance in equal time interval then it is known as Non Uniform Motion.

**Question: 3 sec time is taken by two trains to pass one another when going in the opposite direction but only 2.5 sec if the speed of the one is increased by 50%. What will be the time that one would take to pass the other while going in the same direction at their original speed?**

- 10 sec
- 12 sec
- 15 sec
- 18 sec

**Solution: (3)**

**Download JEE Main Practice Paper**

- The rate of change in the velocity of an object is known as acceleration.
- Acceleration is represented by
- It is a vector quantity.
- SI units are m/s2
- Dimensions of Acceleration are M
^{0}LT^{-2} - Acceleration of an object can be Negative, Positive or Zero

**Uniform Acceleration:** When the magnitude and direction of the acceleration of a body remain constant during motion it is called uniform acceleration.

**Non Uniform Acceleration:** When the magnitude and direction of the acceleration of a body changes during the motion are called as Non Uniform Acceleration.

**The three equations of motion for an object with constant acceleration are given below. **

- v= u+at
- s= ut+1/2 at2
- v2=u2+2as

where u = Initial velocity, v = Final velocity, a = acceleration, s = displacement, t = time

**Question: Find the acceleration of the stone with respect to Man X and Y.**

- (9.8 m/s2, 9.8m/s2)
- (9 m/s2, 10 m/s2)
- (10 m/s2, 10m/s2)
- None of these

**Solution: (1)**

**Question: A bus starts at Station A from rest with uniform acceleration 2m/sec2.The bus moves along a straight line. Find the distance moved by bus in 10 sec?**

- 150m
- 200m
- 100m
- 250m

**Solution: (3)**

Candidates can have a look at the Variation of Displacement, Velocity, and Acceleration with respect to time for different types of motion.

Motion | Displacement(x) | velocity(v) | Acceleration(a) |
---|---|---|---|

At Rest | |||

Motion with constant velocity | |||

Motion with constant acceleration | |||

Motion with constant deceleration |

- There are two types of Quantities in vector i.e. Scalar or Vector
**Scalar Quantity:**Physical quantity that cannot be associated with direction but has magnitude is known as a scalar quantity.**Vector Quantity:**Physical quantity that has both direction and magnitude and also follows or obeys triangle law of addition is known as a vector quantity.

**Unit Vector: **Unite vector is a vector that has unit magnitude and points in a particular direction. In the figure given below, unit vector can be represented as

**Zero Vector or Null Vector:** Zero vector is a vector that has zero magnitudes.

**Equal Vector:** If vector A and B have the same direction and magnitude then they are equal vectors.

**Collinear Vector:** Two or more vectors that are parallel to the same line irrespective of their magnitudes and direction are called collinear vectors.

- Vector addition is commutative-
- Vector addition is associative-
- Vector addition is distributive-

**Question: A vector a→ is turned without a change in its length through a small angle dθ.The value of |Δa→| and Δa are respectively____?**

- 0, a dθ
- a dθ, 0
- 0, 0
- None of these

**Solution: (2)**

**Question: A force F−→=−K(yi^+xj^) (where K is a positive constant) acts on a particle moving in the x-y plane. Starting from the origin, the particle is taken along the positive x- axes to the point (a, 0) and then parallel to the y-axes to the point (a, a). The total work done by the forces F−→ on the particle is____?**

- −2Ka2
- 2Ka2
- −Ka2
- Ka2

**Solution: (3)**

**Check Gujarat Board Released Question Banks for JEE Main**

Candidates can make a study plan for the last 45 days. During the last days, most of the candidates are almost done with their syllabus and are planning to start the revisions. Your revisions also need to be planned so that you can cover all the topics. So here we have prepared a 45 days study plan for JEE Main Physics and if you find it helpful then you can create a similar plan for all other sections also.

Weeks | Activity |
---|---|

Week 1 (June 7 to 14) | Pick one to two topics daily and give 1-hour each to go through the basics and other details of the topics. Do not pick topics that you have left during the time of preparation. |

Week 2 (June 14 to 20, 2020) | After revising the basics you have to learn or go through all the topic wise formulas. Try to write and learn. |

Week 3 (June 21 to 27, 2020) | Solve at least 30-40 questions within 1 to 2 hours. You can repeat the same activity 1 to 2 times a day. |

Week 4 (June 28 to July 4, 2020) | Take the previous year’s papers. Pick one Topic and Identify the questions based on that topic. Try to identify and solve questions from at least 10 questions papers within 1 to 2 hours to improve your speed. |

Week 5 (July 5 to 11, 2020) | Take the Mock Tests daily. |

Week 6 (July 12 to 17, 2020) | Go for Last and Final Revision. |

JEE Main Exam Week (July 18 to 23, 2020) | Go through the detailed paper analysis of ongoing papers. |

**Question: A boat with a speed of 5 km/h in still water crosses a river of width 1km along the shortest possible in 15 minutes. Find the velocity of the river in km/h in the shortest time?**

**Tip to Solve the Question:** It is given that you have to find the velocity in km/h then first of all you have to convert your time that is given in minutes into hours then after applying the formula calculate your answer.

**Solution:** 3km/h

**Question: In 1.0 sec a particle goes from point A to point B, moving in a semi-circle of radius 1.0 m. The magnitude of the average velocity is____?**

**Tip to Solve the Question:** Draw a rough sketch for better understanding. It is a direct question where you have to apply the formula of average velocity.

**Solution:** 2m/s

**Question: A ball is dropped vertically from a height d above the ground. The ball hits the ground and bounces up vertically to the height d/2. Neglect the subsequent motion and air resistance. The velocity v varieties with height h above the ground as_____?**

**Tip to Solve the Question:** You have to understand from the question that initial velocity is downwards and therefore it is negative. After the collision, the original direction is reversed by a smaller magnitude. Also, the velocity is upwards. Now you have check that these conditions are fulfilled by which graph and that will be your answer.

**Solution:** (a)

- Remember to define the axes as per your convenience. This should be only done if the axes are not given in the questions otherwise you have to solve the question as per the axes given.
- Try to solve all the quantities of that question around the axes.
- Always take of positive (+) and negative (-) values or quantities. One small mistake can lead you towards wrong answer.
- Apply the equations of motion along axes separately to find your answer.

- Speed = Distance Travelled/ Time Taken
- Velocity = Displacement/ Total Time
- Average Speed or Average Velocity
- Instantaneous Speed or Velocity
- Acceleration
- v= u+at
- s= ut+1/2 at2
- v2=u2+2as
- Vector addition is commutative-
- Vector addition is associative-
- Vector addition is distributive-

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