poptarts12345
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That's what I find confusing with these types of questions also, can someone explain it please?Also why is the equation 3a=T-3gsin θ instead of 3a=3gsin θ -T
Btw what textbook are you using?Hey, could someone explain to me what tension is and does it oppose motion.
For example in this question :
Is tension moving up the rope from the pink block or down the rope to the pink block?
Also why is the equation 3a=T-3gsin θ instead of 3a=3gsin θ -T
View attachment 29594
its from cambridge ext 1Btw what textbook are you using?
Tension acts away from the pink object, always acts away from objects which are being pulled. You can't push with tension.Hey, could someone explain to me what tension is and does it oppose motion.
For example in this question :
Is tension moving up the rope from the pink block or down the rope to the pink block?
Also why is the equation 3a=T-3gsin θ instead of 3a=3gsin θ -T
View attachment 29594
this looks like Cambridge mx1Btw what textbook are you using?
why is tension larger than 3gsinthethaTension acts away from the pink object, always acts away from objects which are being pulled. You can't push with tension.
3a = T-3gsintheta is a sum of forces.
Net force is 3a. This is from 3g sintheta (its weight acting down the ramp) and T which is tension acting opposite to 3g sintheta.
Since its moving upwards with 3a, obviously weight force has the negative sign and T has the positive sign.
3a up the plane. 3a >0.why is tension larger than 3gsinthetha
wait so if acceleration is up the plane then tension is greater than mg and when acceleration is down the plane tension is smaller than mg?3a up the plane. 3a >0.
An easier way to think of this is that if the directions are the same then they are positively related and if they are opposite then they are negatively related.wait so if acceleration is up the plane then tension is greater than mg and when acceleration is down the plane tension is smaller than mg?
so if the question about a dropping ball attached to a string, the acceleration is moving downwards so tension would be smaller?
ugh why do they need to add phys to maths
The block accelerates in one dimension - either up or down the plane.wait so if acceleration is up the plane then tension is greater than mg and when acceleration is down the plane tension is smaller than mg?
normally we can choose the positive direction, but here its clearly stated 3a is up, so @poptarts12345 use the given direction for this q.The block accelerates in one dimension - either up or down the plane.
The numbers we use to describe acceleration are also one dimensional - either positive or negative.
It's simply a matter of choosing which plane direction is "positive" and which one is "negative".
The choice itself doesn't matter - you just need to be consistent.
The question says acceleration is up the plane, which is a suggestion that we should pick "up the plane" as positive.
In this case, tension is positive (pulling the block up the plane) and gravity is negative.
.
You are also perfectly free to choose "down the plane" as positive acceleration. Then your equation becomes
.
This is essentially the same thing - the only difference is the sign of will be flipped.
(You can make the substitution to see for yourself.)
So if you got with the first equation, you would get with the second.
This is of course what we expect - the block is either moving up or down the plane, so if we change our choice of which direction is "positive" then the acceleration will flip signs so that the block is still physically moving in the same direction.
That is, if with the first equation it means that the block is moving up the slope, as we have chosen a positive number to correspond to moving up the slope. If we instead choose a negative number to correspond to moving up the slope (which is the second equation), then we should expect to find .
Note that the magnitude of and are always the same for this scenario. One becomes (greater than/smaller than) the other only because their signs flip when you change your choice of direction for positive acceleration.
The question only says the object is accelerating m/s up the plane.normally we can choose the positive direction, but here its clearly stated 3a is up, so @poptarts12345 use the given direction for this q.
Tension is a property of taut strings/ropes etc. that pull attached objects towards each other.Hey, could someone explain to me what tension is and does it oppose motion.