5 Common Mistakes in Physics #jee #neet #shorts #mechanics

5 Common mistakes in physics | 5 blunder in jee physics | mechanics common mistakes

#shorts #iitjee #physics #mechanics #mistakes #concept #eduniti #jee2023 #neet #science #jee2024 #jeeadvanced #mohitgoenka #reels #motivation #iitmotivation

[mohitgoenka]

👉Answer:
1. Here Loss in Gravitational PE is same as work done by gravity. You can't write both in same equation. Either you use Work done by conservative forces or use its Potential energy

2. In e=0 velocity of particles just after collision is same but that doesn't mean they will stick to each other. Sticking happens if the question says so (material might be sticky in nature)

3. Centripetal Force is talked about when system is observed from ground frame whereas centrifugal forces (a pseudo force) is considered when system is observed from non-inertial frame (rotating frame ins this case). So there is no point of saying they can balance each other.

4. Here there is no friction between 2kg and 5kg. Best would be to draw FBD of 5 kg block separately. You would clearly see acceleration is 10/5 = 2 m/s2

5. Rolling means no relative motion at point of contact. Means bottom most point of sphere and plank speed must be same. Thus condition should be V1 - wR = V2

[NikhilKumar-zgn]

Ye sun ke mujhe jaha doubt nahi tah, waha ab doubt aana suru ho gaya hai😅😅

[knowledgeisthepower]

1- loss in PE is work by gravity
2 -e=0 means v will be same
3- centripetal force is in ground frame while centrifugal force is in rotating frame
4 - we cannot take 5 kg and 2 kg as system
5 - condition of rolling is point of contact have same velocities it is not necessary that it should be 0

[divyanshugupta]

Aise doubt vale video bnate rahie sir, bahut help hoti h
Thank you so much sir ❤

[blurofficial]

1.Work itself means the transfer of energy, so in the first illustration the lost in the gravitational potential energy gets converted into kinetic energy of the particle as long as there no air resistance.

2. Coefficient of restitution =0, does not necessarily means that the particles will stick together every time, its just the ration of velocities, where does it say that they will stick together. It depends on various other factors such as forces between them, adhesive forces. etc.

3. The centrifugal force is a pseudo force which acts when we see the particle from a non-inertial frame for instance in this illustration we will centrifugal force when the observer is on the particle. The centripetal force can be any force that's acted upon the particle that accelerates the particle towards the centre, its a ground frame force that means when we see the particle from the ground frame we say there's some force by virtue of it the particle is under circular motion that force is called a centripetal force, Its not a new force any force can be centripetal for example mutual gravitational force, electrostatic force, etc.

4. The illustration is quite good, we need to observe the upper block, we will observe that there no horizontal force acting on it so it will be there the whole time as long as the lower block is there once the lower block is gone it will fall down only changing its y coordinates. And when we see the lower block we see that 10N force is acting upon it in the horizontal direction so its acceleration will be A = 10/5 = 2m/s^2 . Just by drawing simple FBDs for both the blocks you will observe that there's no force on the lower block which is in the opposite horizontal direction of 10N force as surfaces are frictionless.

5. In this illustration, the correct Equation should be V1- Omega*R = V2. Because when the relative Velocity of point touching the roller and plank is zero, V2 =0. Then we can use V1 = R*Omega Happily.
Thank you.

[preetirawat]

2.one is actually good question..e=0 does not necessarily mean that particle will stick...it simply means that velocity of seperation is zero...their sticking depends on adhesive forces as well....here the velocity of seperation just after collision is zero that's why with same velocity one does circular motion while other free falls

[rinijn]

In 3rd, Centripetal force is seen with respect to ground frame and Centrifugal force is seen with respect to rotating frame. So we cannot cancel them as they are from different frames.

[gouravgarg]

In 4th one the coefficient of friction is 0.So if we put force on 5kg box the 2kg box will slide down and fall. Then only 5kg will move and acceleration of 5kg will 2m/s2

[itsme.]

1.Gravitational force is conservative force and the change in potential energy comes due to gravitational force. So why would we further take work done by gravitational force?

[paarth]

1. gain is KE is due to +ve WD by mg(conservative force) ...PE is -WD by gravity i.e. it's just another way of writing WET
2 e=0 doesn't mean sticking
It means that normal component of velocity same(velocity in direction on common normal)
3 both forces can't act simultaneously centrifugal force is a pseudo force .
4 draw fbd of each block
Upper block will remain at rest as no ext force in x dir
While lower block is experiencing only 10N force in +ve x dir so acc is 2 in same direction
5 . For rolling there should be no relative motion b/w surface and object so V1-V2=rw is the condition for pure rolling

[vishal.saxsux]

1. Gravity is a conservative force, So work done by it us the change in P.E.
2. Velocity of separation is zero, also e is derived from Impulse. Not neccesarily velocities.
3. There is a centripetal accn towards the centre
4. 2kg block will not even move in horizontal as there in no external force acting on it. It will just falling down once it loses contact with the other block.
5. Rigid body dynamics hmesha se weak tha, mai bs classroom egs padhke gya tha usme

[NishantKumar-yhuw]

3rd one centrifugal force is a pseudo force in the frame of observer who is being sitted on object which is in circular motion. But if we are in ground frame we will not observe any force other than centripetal force. Meanwhile centripetal force is the cause which make object to stay in circular motion.

[FriendsForever-]

Sir jub u tube p divert hota h tab only our 1 short video track per Vapas le leta thanks

[krishnasdance]

centripetal force is for inertial frame and centrifugal force acts in non inertial frame

[vikash]

1.Lose in PE= work done by gravity
2. Same Doubt?
3.Fcentripetal is real while Fcentrifugal is pseudo
4. As friction coefficient 0 b/w blocks, F=5a or a=F/5
5. No because the surface in contact (plank) not in rest, v2=v1-wr

[sarthakghadge]

Because 1st gravity is conservative 2nd collision is inelastic not completely inelastic 4th depends on observer centripetle if observer at inertial frame and centrifugle if observer at non inertial frame

[hemangshrimali]

3. Centipital force is from inertial frame and centrifugal is from non inertial

[xqtkjz]

For without slipping rolling condition is
V rel =v1-v2=rw

[hemangshrimali]

1) -W(conservative) = change in potential energy
There is no non conservative force so... W consevative = change in kinetic energy (WEP)
So. Loss in P. E = Gain in K. E

[gyanzone]

Sir 2nd wala nhi hua tha baki to pta tha ... thankyou sir for these type of videos❤