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# Velocity, Acceleration and velocity time graphs

1. Hi guys,

Im really really struggling with physics and I was wondering if any of you could help me with it or even have good ways of learning it. The subjects I'm struggling with are velocity, acceleration and velocity time graphs. Please help!!!!
2. What is it about velocity, acceleration and VT Graphs that you don't understand? Is it the equations or what they actually are? Or what different parts of the graph mean? 21 questions I know, lmao.

I learn by watching videos on Youtube and making notes. Just type something like 'AQA P2 Revision' and there should be a whole cluster of videos that help, assuming the exam board you're doing is AQA.
3. (Original post by chloe_armstrong_)
Hi guys,

Im really really struggling with physics and I was wondering if any of you could help me with it or even have good ways of learning it. The subjects I'm struggling with are velocity, acceleration and velocity time graphs. Please help!!!!

When it comes to speed-time graphs, it is useful to know that the gradient of the lines on that graph represent acceleration.
4. As soon as I get back from school I will thank you so much !
5. (Original post by RDKGames)

When it comes to speed-time graphs, it is useful to know that the gradient of the lines on that graph represent acceleration.
These are the sorts of questions I mean xx
6. (Original post by RDKGames)

When it comes to speed-time graphs, it is useful to know that the gradient of the lines on that graph represent acceleration.
Theses are the sorts of questions I mean. Thank you xx
7. (Original post by chloe_armstrong_)
Theses are the sorts of questions I mean. Thank you xx
Any particular question you're stuck on?
8. (Original post by RDKGames)
Any particular question you're stuck on?
if I'm quiet honest majority of them :/ but the first once really stumped me xx
9. (Original post by chloe_armstrong_)
if I'm quiet honest majority of them :/ but the first once really stumped me xx
Most of these aren't anything to do with speed-time graphs, but what's your approach to the first one??

You need to know that when acceleration is 0, the net force is 0 due to so the two things are either stationary or going at a constant speed.

If one force is greater than the other, then there is acceleration therefore the objects are increasing in speed and definitely moving.
10. (Original post by RDKGames)
Most of these aren't anything to do with speed-time graphs, but what's your approach to the first one??

You need to know that when acceleration is 0, the net force is 0 due to so the two things are either stationary or going at a constant speed.

If one force is greater than the other, then there is acceleration therefore the objects are increasing in speed and definitely moving.
i would usually think that the tractor is moving because it says the tractor and trailer are accelerating,i so would assume that "A and B are the same" However i have no idea if this is right.
11. (Original post by chloe_armstrong_)
i would usually think that the tractor is moving because it says the tractor and trailer are accelerating,i so would assume that "A and B are the same" However i have no idea if this is right.
It is not. If there is acceleration, then there is a net force which is not 0. And if the net force is not 0, therefore the two forces do not balance; hence they are not the same.

As I said, take where is the net force. We know that . If it is accelerating then which means that (because the mass cannot be 0, and neither can the acceleration). Since we know that therefore which means that A and B cannot be equal to one another. If they were, we would get 0 and that is not allowed from our calculations.

One of them must be greater than the other.
12. In a general sense, you can remember (as said above) that acceleration is the slope of the velocity curve. Also, velocity is the slope of the position curve. Derivatives are just slopes. Therefore, if you're having trouble remembering the formulas for each, learn how to take the derivative of a polynomial equation, and the reverse. (It is calculus, but the technique for this particular kind of function is easily learned.) If you know what acceleration is (because of gravity, or some other thing), you will be able to work that back into a velocity function, and then the position vs time graph.

I remember having a lousy teacher for 11th grade physics and going nuts trying to learn these equations for weeks in fall term, only to be surprised by how easily we powered through them in maybe 15 minutes during spring term in calculus.
13. (Original post by RDKGames)
It is not. If there is acceleration, then there is a net force which is not 0. And if the net force is not 0, therefore the two forces do not balance; hence they are not the same.

As I said, take where is the net force. We know that . If it is accelerating then which means that (because the mass cannot be 0, and neither can the acceleration). Since we know that therefore which means that A and B cannot be equal to one another. If they were, we would get 0 and that is not allowed from our calculations.

One of them must be greater than the other.
Thank you so so much! thats helped a ton!
14. (Original post by Camilli)
In a general sense, you can remember (as said above) that acceleration is the slope of the velocity curve. Also, velocity is the slope of the position curve. Derivatives are just slopes. Therefore, if you're having trouble remembering the formulas for each, learn how to take the derivative of a polynomial equation, and the reverse. (It is calculus, but the technique for this particular kind of function is easily learned.) If you know what acceleration is (because of gravity, or some other thing), you will be able to work that back into a velocity function, and then the position vs time graph.

I remember having a lousy teacher for 11th grade physics and going nuts trying to learn these equations for weeks in fall term, only to be surprised by how easily we powered through them in maybe 15 minutes during spring term in calculus.
Thank you so so much. xx

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