You are right, also it can be because when the object is returning back, it's direction of motion is opposite to the intial motion or velosity. So, the final velocity is negative when it returns, and its magnitude is increasing(getting faster.) But, since our point of reference is the intial motion or intial velocity, we assume both the velocity when it returns back and its acceleration is negative. We can also prove this by calculation: since the final velocity when it returns back is negative, the acceleration becomes negative. a=(vf-vi)/tj
Sir a lot of thanks to you.you just solved the complicated misunderstanding in my mind Thanks a lot. Please keep uploading such videos so every body will benefit from your knowledge.
"Direction of ball" means you are concerned with the direction of velocity. But the question is about direction of acceleration, which is always downward (towards earth's centre), and is the direct result of the gravitational force, which is always downward.
The answer is straight forward. If it drops from a height after initially firing horizontally, the vertical velocity increases, so, a = g; i.e. positive. As has been stated in the explanation, if v increases, a is positive; and if decreases, a is negative.
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same doubt on this concept to me object thrown from some height and that takes projectile motion the what is the value of g upwards and downwards? please clarify @ sapna sharma
g is always positive because g = GM/R^2. In no way that g can be negative. The issue is whether a is positive or not. If v increases, a = g and so positive. If v decreases, a = - g and so negative.
@@sajitchandrashakya in projectile motion when the projectile is moving upward v decrease so a will be negative. But when the projectile start downward motion v increase so a must be positive. But this concept is against to your video concept. Need some explanation
Sir what will be the sign of 'g' when a bullet is fired from a mountain?? It goes in downward direction in projectile motion, so i think it should be positive. M i right??
I saw in one answer that they took g as negative, and put -g in formula of s=ut -1/2 gt^2..... but i think that it should be s=ut + 1/2 gt^2..plz reply
@@sajitchandrashakya thanks sir, but plz tell, if i shot a bullet horizontally from a mountain, i goes down from mountain in projectile motion. so, if i want to find displacement, should i put g as negative or positive in equation i.e s=ut+1/2(-gt^2) or s=ut+1/2gt^2
i have doubt in 1 que. i.e, 2 guns situated on the top of a high hill fire a shot each at some interval of time with the same speed 5 root3 m/s. One gun fires horizontally and other fires upwards at an angle of 60 degree with the horizontal. The shots collide in air at point P. Find i) the time interval between the firing ii) the coordinates of P, taking top of the hill as the origin. sir plz tell me how to take g in this question
Well the force is constant but the thing is we are not talking about magnitude,we are talking about direction.the minus sign.
Very well explained......... The point which u have told "the force remain constant"" ........ Is amazing point to student
Yes, Mr. Subhash. Stressing an important point causes great pleasure. It is a source of great adrenaline rush!!
You are right, also it can be because when the object is returning back, it's direction of motion is opposite to the intial motion or velosity. So, the final velocity is negative when it returns, and its magnitude is increasing(getting faster.) But, since our point of reference is the intial motion or intial velocity, we assume both the velocity when it returns back and its acceleration is negative.
We can also prove this by calculation: since the final velocity when it returns back is negative, the acceleration becomes negative.
a=(vf-vi)/tj
Sir a lot of thanks to you.you just solved the complicated misunderstanding in my mind
Thanks a lot. Please keep uploading such videos so every body will benefit from your knowledge.
Thank you, I will!!!
Thanks a lot for this video sir. This was one doubt that I was stuck with. U cleared this now. thanks a lot sir.
Thank u sir, u just refreshed my mind of thinking the wrong way for Gravity.
Thank so much sir
You've cleared everything 😍✌️
sir force and acceleration is constant but the direction is keep changing and we use this +and - is due to direction
In depth and well explanation
If an apple fall from our hand in the downward direction what will be the acceleration - positive or negative
In this case, a will be positive, because v increases. The increase is from zero to some non zero value!!
Very nic explanation we our nation need more dedicated teacher like you a grand salute to you sir keep it up
@@sajitchandrashakya yes sir your donation in field of education is more powerful than the cring things like race caste etc
Nice sir.. Grt want more videos like this
Sure 👍
Thanks sir for a great explaination i am from delhi and your lecture help me a lot.
Please tell me when we take negative gravity in potential energy formula (mgh)
I am very confused🤔 sometimes we use positive on some times negative
Mr. Dibya, g is always positive. The issue is whether a is positive or negative. If velocity increases, a is positive. If it decreases, a is negative.
,g is always -ve in motion..hope I'm not wrong
You are!!!! Sorry for that!!!
Best explanation sir
Thank you for this sir!!
Wonderful sirr
Great work sir keep it up sir
Om Sairam swamy. God bless you. Sukhibhava
Thanks for the blessings!! My prayers for you!!!
So when g will be positive?
Example like skydiving
Example like skydiving
I finished my alevel still I.love your video.You are truly passionate physician .insalllah god strength you always
@@sajitchandrashakya Always Welcome Sir,
Sir but the direction of ball has been changed ,as applying vacter law, direction change means sign is also changed
"Direction of ball" means you are concerned with the direction of velocity. But the question is about direction of acceleration, which is always downward (towards earth's centre), and is the direct result of the gravitational force, which is always downward.
But initially why did we take a=(-g)
When velocity decreases, a is negative. This happens right from initial moments, so a = -g.
Thank u so much
U explained very well...
Thank you sir 🙏🙏🙏🙏
Most welcome!!!! Too indebted!!!
great video
Sir thankss alot you cleared the mystery. sir but tell what if projectile drops from a height what will be its a? positive or negative?
The answer is straight forward. If it drops from a height after initially firing horizontally, the vertical velocity increases, so, a = g; i.e. positive. As has been stated in the explanation, if v increases, a is positive; and if decreases, a is negative.
@@sajitchandrashakya Okay sir thanks alot.
You didn’t explain why it’s negative. You just said that it’s always negative g
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Sir if in case of projectile motion a body is thrown from some height and that body takes projectile path
What is the value of g
@@sajitchandrashakya thanks for clarifying my concept
same doubt on this concept to me
object thrown from some height and that takes projectile motion the what is the value of g upwards and downwards? please clarify @ sapna sharma
Sir, If a projectile is thrown from a height(horizontal motion projectile) what will be its g.
g is always positive because g = GM/R^2. In no way that g can be negative. The issue is whether a is positive or not. If v increases, a = g and so positive. If v decreases, a = - g and so negative.
@@sajitchandrashakya in projectile motion when the projectile is moving upward v decrease so a will be negative. But when the projectile start downward motion v increase so a must be positive. But this concept is against to your video concept. Need some explanation
Thanks 👍
Thank you sir . You have discussed very clearly
Sir what will be the sign of 'g' when a bullet is fired from a mountain?? It goes in downward direction in projectile motion, so i think it should be positive. M i right??
I saw in one answer that they took g as negative, and put -g in formula of s=ut -1/2 gt^2..... but i think that it should be s=ut + 1/2 gt^2..plz reply
@@sajitchandrashakya thanks sir, but plz tell, if i shot a bullet horizontally from a mountain, i goes down from mountain in projectile motion. so, if i want to find displacement, should i put g as negative or positive in equation i.e s=ut+1/2(-gt^2) or s=ut+1/2gt^2
i have doubt in 1 que. i.e, 2 guns situated on the top of a high hill fire a shot each at some interval of time with the same speed 5 root3 m/s. One gun fires horizontally and other fires upwards at an angle of 60 degree with the horizontal. The shots collide in air at point P. Find i) the time interval between the firing ii) the coordinates of P, taking top of the hill as the origin.
sir plz tell me how to take g in this question
Thanks sir
Thank you so much sir 🙏
Most welcome!!
Thank you so much sir :))
All the best!!
Thank you sir....
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Thank you so much 👏👏
if i would be your student,then i think i would be best physicst.
Haha!! I still expect you to be, even if you are not my student!!!
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Terrible explanation didn’t even explain why just told ki ye line rata Marlo
Thanks a lot sir
Most welcome!!