resolving forces

hey struglling with part bii of question 38.. i couldnt upload the question so i linked the paper and markscheme.
basically, for part bii, it says the horizontal component of T is equal to 9974, which is the same as the horizontal component of P. but when i checked the vertical components of P and T, they aren't equal? so the system cannot be in equilibrium right? if anyone could help out id be so grateful thanks!!!

https://www.physicsandmathstutor.com/pdf-pages/?pdf=https%3A%2F%2Fpmt.physicsandmathstutor.com%2Fdownload%2FPhysics%2FA-level%2FTopic-Qs%2FEdexcel%2F02-Mechanics%2FSet-D%2FMechanics.pdf

https://www.physicsandmathstutor.com/pdf-pages/?pdf=https%3A%2F%2Fpmt.physicsandmathstutor.com%2Fdownload%2FPhysics%2FA-level%2FTopic-Qs%2FEdexcel%2F02-Mechanics%2FSet-D%2FMechanics%2520MS.pdf

(edited 2 months ago)

Reply 1

mqb2766

21

Original post by Nat4695

hey struglling with part bii of question 38.. i couldnt upload the question so i linked the paper and markscheme.
basically, for part bii, it says the horizontal component of T is equal to 9974, which is the same as the horizontal component of P. but when i checked the vertical components of P and T, they aren't equal? so the system cannot be in equilibrium right? if anyone could help out id be so grateful thanks!!!

https://www.physicsandmathstutor.com/pdf-pages/?pdf=https%3A%2F%2Fpmt.physicsandmathstutor.com%2Fdownload%2FPhysics%2FA-level%2FTopic-Qs%2FEdexcel%2F02-Mechanics%2FSet-D%2FMechanics.pdf

https://www.physicsandmathstutor.com/pdf-pages/?pdf=https%3A%2F%2Fpmt.physicsandmathstutor.com%2Fdownload%2FPhysics%2FA-level%2FTopic-Qs%2FEdexcel%2F02-Mechanics%2FSet-D%2FMechanics%2520MS.pdf

If you consder the vertical forces acting on the wheel, theyre (approximately) zero so
weight + T vertical = P vertical

Reply 2

Nat4695

OP

13

thanks! Do you have any advice on how to spot these sort of things? I’m pretty solid in theory in general but it seems to escape my head sometimes when I look at a question that feels unfamiliar or challenging

Reply 3

mqb2766

21

Original post by Nat4695

thanks! Do you have any advice on how to spot these sort of things? I’m pretty solid in theory in general but it seems to escape my head sometimes when I look at a question that feels unfamiliar or challenging

For an object to be in equilibrium you have to balance the forces acting on that body. Here, the horizonntal forces are equal (and opposite, N3) because you consider the horizontal forces acting on the wheel (in equilibrium). Similarly for the vertical forces acting on the wheel.

The boring advice is to do Newton carefully. Pick the object, sketch the forces acting on it, work out their directions/signs and equate.

Note if both the horizontal and vertical componennts of the two forces were equal, then the two forces would be equal which clearly theyre not.

(edited 2 months ago)

Reply 4

Muttley79

20

Original post by Nat4695

thanks! Do you have any advice on how to spot these sort of things? I’m pretty solid in theory in general but it seems to escape my head sometimes when I look at a question that feels unfamiliar or challenging

Good large diagram and remember all the forces acting in the given direction.

I don't think there's anything particularly different about this question.

resolving forces

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