Need help with the interpretation of this v(t) graph

[gladidi]

Summary:: Please tell me an example

Determine the distance traveled by the object between 0-7 s.

Determine the acceleration of the piece in the range of 0-4 s
Determine the acceleration of the piece in the range of 4-7 s.I've tried, but something I'm doing wrong. Could you clarify?

 

[berkeman]

Welcome to PF.

You need to show us your work before we can help you with this. How is the velocity as a function of time related to the position and acceleration as a function of time? How can you use that to help you solve these questions?

 

[gladidi]

Welcome to PF.

You need to show us your work before we can help you with this. How is the velocity as a function of time related to the position and acceleration as a function of time? How can you use that to help you solve these questions?

This is the work.

 

[berkeman]

This is the work.

No, that is the graph you are supposed to use to figure out those 3 questions.

Please answer this:

How is the velocity as a function of time related to the position and acceleration as a function of time?

 

[gladidi]

No, that is the graph you are supposed to use to figure out those 3 questions.

Please answer this:

I've tried to solve it with a chart, but the answers aren't going right

 

[berkeman]

You didn't answer my questions. Until you do that, you will not get very far on problems like this one...

 

[berkeman]

How is velocity defined in terms of position and time?

How is acceleration defined in terms of velocity and time?

 

[robphy]

Summary::
I've tried, but something I'm doing wrong. Could you clarify?
View attachment 288876

What specifically did you try?

I've tried to solve it with a chart, but the answers aren't going right

What approach with a chart did you try?
What were your answers
and how did you get them, specifically?

 

[gladidi]

What specifically did you try?What approach with a chart did you try?
What were your answers
and how did you get them, specifically?

> Determine the acceleration of the piece in the range of 0-4 s

< 12/4

 

[robphy]

> Determine the acceleration of the piece in the range of 0-4 s

< 12/4

Ok, that's a start.
Why 12/4?

 

[gladidi]

Ok, that's a start.
Why 12/4?

Speed change / time to change

 

[gladidi]

Ok, that's a start.
Why 12/4?

Acceleration formula

 

[robphy]

Speed change / time to change

That sounds like a slope.
What is the speed-change [although velocity-change is more correct], during the time-change?

 

[haruspex]

Speed change / time to change

What is the speed at t=0s?
What is the speed at t=4s?
What is the change in speed?

 

[gladidi]

What is the speed at t=0s?
What is the speed at t=4s?
What is the change in speed?

Speed at t=0s =0?
Speed at t=4s? =12?

 

[haruspex]

Speed at t=0s =0?

Not according to the graph.

 

[gladidi]

Not according to the graph.

It is 3?

 

[haruspex]

It is 3?

Yes.

 

[gladidi]

Yes.

finally i got this right..

 

[gladidi]

What is the speed at t=0s?
What is the speed at t=4s?
What is the change in speed?

How solve this? Determine the acceleration of the piece in the range of 4-7 s.

 

[haruspex]

How solve this? Determine the acceleration of the piece in the range of 4-7 s.

Same process. What was the increase in velocity in that interval?

 

[gladidi]

Same process. What was the increase in velocity in that interval?

4 and 7 have same speed 12?

 

[haruspex]

4 and 7 have same speed 12?

Yes, so what was the increase in speed?

 

[gladidi]

Yes, so what was the increase in speed?

24?

 

[haruspex]

24?

If you are earning $20 an hour and that changes to $20 an hour, how much is your pay rise?

 

[haruspex]

I give up

 

[gladidi]

If you are earning $20 an hour and that changes to $20 an hour, how much is your pay rise?

0...

 

[haruspex]

0...

Right.
So what is the speed increase from t=4s to t=7s?

 

[gladidi]

Right.
So what is the speed increase from t=4s to t=7s?

Answer is 0..

 

[gladidi]

The last point is to calculate the distance traveled by objects.
it is said that should calculate the surface area

 

[haruspex]

The last point is to calculate the distance traveled by objects.
it is said that should calculate the surface area

Yes, in a velocity-time graph the distance traveled is given by the 'area' under the graph line. But the area of each square means the product of the coordinate intervals.
Here, the vertical grid lines are at 1 second intervals and the horizontal grid lines at intervals of 2m/s, so each little square represents 1 second x 2m/s = 2m.

 

[gladidi]

Yes, in a velocity-time graph the distance traveled is given by the 'area' under the graph line. But the area of each square means the product of the coordinate intervals.
Here, the vertical grid lines are at 1 second intervals and the horizontal grid lines at intervals of 2m/s, so each little square represents 1 second x 2m/s = 2m.

Is this right way to solve this? example 35*2+8/2*2?

 

[haruspex]

Is this right way to solve this? example 35*2+8/2*2?

That is the right answer. I cannot tell whether you are expected to do it by counting squares are algebraically. I would use standard formulae for areas of rectangles and triangles.

 

[gladidi]

That is the right answer. I cannot tell whether you are expected to do it by counting squares are algebraically. I would use standard formulae for areas of rectangles and triangles.

35*2+8/2*2? is 78m but it's not right..

 

[haruspex]

35*2+8/2*2? is 78m but it's not right..

You want the distance for the whole 8 seconds, right?
In the first 4 seconds the average speed is (3+12)/2=7.5m/s. Over four seconds that covers 30m.
For the remaining 4 seconds the speed is 12m/s, giving a distance of 48m.
30m+48m=78m.