Its positive because he choose it to be- you could call it negative- physics has no absolute +/- anywhere in any system... you pick your convention and stick with it through the problem.. usually choose positive in direction of motion (but you don' t have to).
In the 5kg force diagram there are 3 forces acting pushing the object towards the left (force of friction = 1.96, force of tension= 1.96, and force of friction of the object = 13.72). I don't really understand the difference between force of friction = 1.96 and force of tension = 1.96
only problem i have with this is the free body diagram for the 4kg mass why is the downward direction positive, in your previous examples you didnt do this???.
+oyindenyafa tarakeme I think it's too late to reply this one but just in case.... in my opinion the positive and negative sign didn't follow whether it's heading downward or upwards (like, it is positive if it goes upward or negative for downwards) but it is positive if it follows where the whole system goes. in this video the 4 kg mass causes the whole system to move towards the direction of it's weight(downwards); that's why the 5kg mass moves to the right and 2kg mass to the left. Just imagine the whole thing moves!
This is kinda late, but the friction is resisting the whole system from moving, which means the friction between the stacked blocks happens twice since the system wraps around the pulley, which means the friction between 2 and 5 is 2 ways, it resists two times
@Rajanpanta you are incorrect, the friction would not cancel. You need to understand the positive direction is changed when a pulley is included in the system
Thank you Sir your are one of best I have ever seen. Thumbs up
Its positive because he choose it to be- you could call it negative- physics has no absolute +/- anywhere in any system... you pick your convention and stick with it through the problem.. usually choose positive in direction of motion (but you don' t have to).
very helpful, thank you
In the 5kg force diagram there are 3 forces acting pushing the object towards the left (force of friction = 1.96, force of tension= 1.96, and force of friction of the object = 13.72). I don't really understand the difference between force of friction = 1.96 and force of tension = 1.96
Why would you count 1.96 twice?
excellent
only problem i have with this is the free body diagram for the 4kg mass why is the downward direction positive, in your previous examples you didnt do this???.
+oyindenyafa tarakeme
I think it's too late to reply this one but just in case....
in my opinion the positive and negative sign didn't follow whether it's heading downward or upwards (like, it is positive if it goes upward or negative for downwards) but it is positive if it follows where the whole system goes.
in this video the 4 kg mass causes the whole system to move towards the direction of it's weight(downwards); that's why the 5kg mass moves to the right and 2kg mass to the left. Just imagine the whole thing moves!
thank you so much! this is a life saver
hey!
i think only 1.96N and 13.72N friction forces will counteract with the acc. of 4kg mass.
So why have you used 1.96 as twice?
i'm little confused.
You need to rephrase your question. The acceleration of the 4 kg mass has only T2 in opposition.
Why two -1.96 is used.. its by third law and they should cancel one another or something
Correct me plz
This is kinda late, but the friction is resisting the whole system from moving, which means the friction between the stacked blocks happens twice since the system wraps around the pulley, which means the friction between 2 and 5 is 2 ways, it resists two times
I think for 5kg block there will be only friction force 13.72 .
Not( 13.72+1.96)
No it also has the 1.96 because the block above it is keeping it from moving. It would be 13.72 like you said if there was no block above it
very nice video.
It is absolutly wrong.The frictional force should not be included on 2nd system as it cancles with each other ..........
@Rajanpanta you are incorrect, the friction would not cancel. You need to understand the positive direction is changed when a pulley is included in the system