- #1
TomK
- 69
- 14
- Homework Statement
- The answer is 'C = 0 m/s²'.
- Relevant Equations
- Connected particles?
I don't understand the working shown on the website (seen above).
Firstly, they establish 'up' as the positive direction for acceleration, so A is +4 and D is -4.
They create two points, P and Q, and set acceleration values for them. I understand that connected particles have the same magnitude of acceleration, but I don't understand where they got '2' from.
The question states that B does not accelerate 'relative to the global coordinate system'. I looked-up this phrase, but I don't understand what it means.
This is what they say on the website: "The left-hand side of the system has two constraints: 'A = 4 m/s²' and 'B = 0 m/s²'. Looking at point P, these constraints mean that, for every 2 units that A rises in height by, point P rises by 1 unit." I don't know how they came to this conclusion.
Then, they say: "hence, the absolute acceleration of the connecting string is 2 m/s², so P = 2 m/s²." Again, why is it 2? I understand that Q must then be -2, but I don't get why P = 2m/s² in the first place.
I don't understand this question at all. Please help.