Finding Velocity on a Position/Time Graph

  • Thread starter Thread starter 5pirit
  • Start date Start date
  • Tags Tags
    Graph Velocity
AI Thread Summary
To find velocity on a position/time graph, it's essential to calculate the slope correctly. The slope represents velocity, and for a straight line, it should remain constant. The formula Vf-Vi/Tf-ti is meant for calculating average velocity, not acceleration. If different calculations yield varying results, it indicates a miscalculation in determining the slope. Ensuring consistent points are used from the graph will help achieve the correct velocity value.
5pirit
Messages
1
Reaction score
0
Hey everyone, I'm having trouble finding velocity on a straight line position/time graph. Every single equation I do ends up with a different answer, which doesn't make sense because it's a straight line.

I know the equation is

Vf-Vi/Tf-ti

The answer to this question is 1.4m/s N

Example:

45-25/28-16= 1.666666m/s Wrong answer. I'm just taking these from the graph by the way.

25-20/16-14= 2.5, completely different answer.

Could someone please explain what I'm doing wrong? I'm calculating the slope which seems to change with every calculation that I do, which I understand is wrong.
 
Physics news on Phys.org
Try to post the graph so we can see it. Also, if your v is velocity, you are dividing a velocity change by an elapsed time. That gives acceleration. If you want velocity, divide displacement by time.
 
5pirit said:
Hey everyone, I'm having trouble finding velocity on a straight line position/time graph. Every single equation I do ends up with a different answer, which doesn't make sense because it's a straight line.

I know the equation is

Vf-Vi/Tf-ti

The answer to this question is 1.4m/s N

Example:

45-25/28-16= 1.666666m/s Wrong answer. I'm just taking these from the graph by the way.

25-20/16-14= 2.5, completely different answer.

Could someone please explain what I'm doing wrong? I'm calculating the slope which seems to change with every calculation that I do, which I understand is wrong.
Hello 5pirit. Welcome to PF !

What is the slope of that line?
 

Thread 'Struggling to understand the concept of this question (ice cube in water optics question)'

TL;DR Summary: I came across this question from a Sri Lankan A-level textbook. Question - An ice cube with a length of 10 cm is immersed in water at 0 °C. An observer observes the ice cube from the water, and it seems to be 7.75 cm long. If the refractive index of water is 4/3, find the height of the ice cube immersed in the water. I could not understand how the apparent height of the ice cube in the water depends on the height of the ice cube immersed in the water. Does anyone have an...
View full post »
Thread 'Variable mass system : water sprayed into a moving container'

Thread 'Variable mass system : water sprayed into a moving container'

Starting with the mass considerations #m(t)# is mass of water #M_{c}# mass of container and #M(t)# mass of total system $$M(t) = M_{C} + m(t)$$ $$\Rightarrow \frac{dM(t)}{dt} = \frac{dm(t)}{dt}$$ $$P_i = Mv + u \, dm$$ $$P_f = (M + dm)(v + dv)$$ $$\Delta P = M \, dv + (v - u) \, dm$$ $$F = \frac{dP}{dt} = M \frac{dv}{dt} + (v - u) \frac{dm}{dt}$$ $$F = u \frac{dm}{dt} = \rho A u^2$$ from conservation of momentum , the cannon recoils with the same force which it applies. $$\quad \frac{dm}{dt}...
View full post »

Similar threads

Finding acceleration from Velocity vs Position graph
Replies
2
Views
4K
Find velocity-time equation from velocity-position equation
Replies
11
Views
2K
What is the relationship between velocity and time on this graph?
Replies
9
Views
2K
Calculate the Acceleration of this Car
Replies
7
Views
986
Inconsistency in a Velocity-Time Graph
Replies
13
Views
3K
Analyzing Motion: Deriving Displacement Graphs from First Principles
Replies
6
Views
2K
Finding the change in velocity from an acceleration vs time graph
Replies
1
Views
3K
How to find an average acceleration using an average velocity?
Replies
5
Views
1K
Position from velocity time graph
Replies
4
Views
4K
What is the intersection point of two objects on a position vs time graph?
Replies
10
Views
2K

Hot Threads

Recent Insights

Back
Top