Physics - Moving About - Velocity Motion Graphs help? (1 Viewer)

[chlololoco]

Okay, so I've been understanding this topic for the most part, but I just seem to fail at interpreting the graphs.. Any advice? or know something that might dumbify it?

Thankyou so much!

 

[nerdboy27]

What exactly are you struggling to interpret?
I myself just follow a few basic rules, which can be used for most questions.
The area underneath the curve is equal to displacement in a velocity - time graph and velocity in and acceleration time graph.
The gradient represents the velocity on a displacement-time graph and represents acceleration on a velocity-time graph.
If the curve is parabolic on a displacement time graph, acceleration is constant.
Any stationary points on a displacement time graph is where the body is at rest. Any stationary point on a velocity time graph is where the body is experiencing no acceleration. Most questions just refer to these principles.

 

[chlololoco]

I understand the area under the curve, I think it's just the gradient bit haha? i'm not sure.. it's just confusing? like the maths parts of the course and the theory I'm good at and understand but for whatever reason (maybe because I was away on the day) I just don't get them...
but thankyou anyway because you've helped

 

[Sy123]

Once you do HSC 2U Math everything will become very very clear. But for now, here is the gradient concept.

A gradient is essentially the rate of change of something. Rise over Run is simply the amount of Rise there is per unit of Run, per se. The higher the gradient (i.e. the steeper upwards) the faster the y-value is changing in respect to the x-value (if we are talking about cartesian plane). In retrospect, with displacement, the higher the gradient of a displacement-time graph, the higher the rate of change of displacement with respect. And what do we learn by definition? That velocity is the rate of change of displacement in respect to time.

Therefore velocity is the gradient of a displacement-time graph.

Moreover, the gradient of a velocity-time graph is the acceleration, since by definition, acceleration is the rate of change of velocity, therefore the rate of change of the velocity-time graph is the gradient, which is then the acceleration.

With this knowledge, it is possible to comment on the velocity and acceleration given their respective graphs. If the gradient of the graph of a displacement-time graph is 2 for instance, then the velocity is 2.
Now, for instance if they give you a displacement-time graph, and they ask you to find when the particle is at rest. You must look for the time when the graph has a gradient of zero, since in a displacement-time graph, when the gradient is zero, the velocity is then zero, hence the particle (object/body) is at rest. The part where it has a gradient of zero, is where the displacement-time graph is horizontal. (You know, a gradient of zero)

If they ask for instance, when is the velocity positive, then yuo give the times when the displacement-time graph's gradient is positive, which is when it is increasing, i.e when it is sloping upwards.

I think thats it for the gradients aspect of it, again, once you do HSC 2U Math, then this will be all understood easily, (or even when you do Calculus in Preliminary)

Does your school/teacher give you curves as graphs as well? If so then I need another post to explain that concept.

 

[chlololoco]

Does your school/teacher give you curves as graphs as well? If so then I need another post to explain that concept.

Sorry for the late reply, but yeah they do