IIT JEE , AIEEE Forum - Physics , General

kane

whenever two vectors are equal in magnitude and the angle b/w them is 120 degrees then the magnitude of resultant is also same as the 2 vectors.

conversely,if the 2 vectors and their resultant have the same magnitude the angle is 120 degrees.

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mukulss

i thank all the people who have replied to this post.
actually i was off line 4 4 days.
if anyone wants 5 more points post a new concept from anywhere.
thank u kane and water demon.

spideyunlimited

for a body undergoing free fall,
the ratio of distances covered in 1st second , 2nd second, 3rd second and so on .. is:
1 : 3 : 5 :7.....odd numbers

vivsarda

We can conserve angular momentum wen body is revolvin around the other like planets abt the center of the planet as no external torque is acting abt that point ..

tarunsssss

THE PRODUCT OF AREA OF CROSS SECTION AND THE SPEED REMAINS SAME AT ALL POINTS OF ATYBE OF FLOW

frenied

when considering ques in rotational motion involving friction..until and unless frictional force is especially aksed..its most useful to consider the motin about the point of contact with the ground.it has 2 advantages-
1) u get rid of the friction crap and the problem of deciding its direction
2)u dont have to think much of the translational velocity.u get only a rotational velocity which is much easier to deal with.

iitjee08aspirant

best method to solve a mech question is to use work done =change in kinetic energy as it is applicable even in non inertial frame!!!

karthik2007

Bernoulli's equation is the analogue of work energy theorem for fluids. It can help you in almost any situation, when you are asked to find the pressure, velocity, etc of a particular fluid flowing through a material.

kane

remember,in questions concerning pulleys,you can find the common acc. of the system using the shortcut method that common acc. is equal to the ratio of net external force to the total mass.

e.g. two masses are there of 4kg and 2 kg. acc. will be (4-2)g/6 which is equal to 20/6= 3.33 m/sec².

the long method is 4g-T=4a and T-2g=2a

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kane

always remember that in a vertical circle for uniform motion no matter what the velocity is,difference in tensions at the lowest and the highest pts. is 2mg whereas for non-uniform motion it's 6mg

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harsha_27

1.FERMI'S THEOREM .......if a body is acted upon by three forces and is in equilibrium.....then F1/SinA = F2/SinB = F3/ SinC where A is angle b/w F2 AND f3 ,B is the angle b/w F1 and F3 and C is the angle b/w F1 and F2
2.+I effect is very small compared to -I effect.....if in a molecule two effects are present then -I effect dominates +I effect.
3.DELTA STAR TRANSFORMATION IN RESISTORS (NOT IN IIT SYLLABUS BUT THIS SHORT CUT METHOD SAVES TIME)......
if in any circuit if three resistors R_a , R_b , R_c are connected in a triangular order as shown in figure ....we can always replace them with equivalent resistances R₁ ,R₂, R₃ so that equivalent resistance b/w the points N₁ ,N₂ , N₃ is unaltered......this is a very easy and time saving method to find out equivalent resistance in large circuits by converting the triangles to delta forms and hence simplifying the circuit..here R₁ =R_a R_b/R_a+R_b+R_c ,R₂ = R_b R_c/ R_a+R_b+R_c,R ₃=Ra R_c/R_a+R_b+R_c

harsha_27

plz click the above black image to see the actual image......it did not get uploaded properly.....but u can click on it and see it...ok

talk2pratyush

if a particle is thrown vertically upwards...distance travelld by in its last second of journey is 5metres....irrespective of its mass.

kane

remember if a circle touches the x-axis then c=g² and if it touches the y-axis then c=f²

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