Velocity vs time and acceleration vs time

In summary, the net force needed to produce the velocity vs time and acceleration vs time graphs described is determined by the direction and rate of change of the velocity and acceleration. Velocity, being a vector, can have a negative magnitude while still increasing in the negative direction. Acceleration, being related to force by mass, will always have the same sign as the force. Understanding the relationship between velocity and acceleration can help determine the direction and magnitude of the net force.
  • #1
pb23me
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Homework Statement


describe the net force needed tto produce the following velocity vs time and acceleration vs time graphs.
i don't have a pic so I am goin to explain... velocity vs time starts below the x-axis and increases at a constant rate to some point above the x axis. at that point velocity is then a horizontal line. accleration vs time starts above the x-axis and decreases at a constant rate to some point below the x axis. these are just two questions on a test that i got wrong.

Homework Equations





The Attempt at a Solution

 

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  • #2
hi pb23me! :wink:

show us what you tried, and then we'll know how to help! :smile:
 
  • #3
well I am just confused about when velocity was in the neg direction and slowing dwn i put neg force. also on the acceleration vs time i have no clue what's going on with the force when there is a line starting from the pos side that decreases at a constant rate into the neg side.
 
  • #4
for the acceleration do you say it is a pos force causing it if it is on the pos side and neg force on the neg side? regardless of the accleration line going towards or away from the axis of time??
 
  • #5
hi pb23me! :smile:
pb23me said:
well I am just confused about when velocity was in the neg direction and slowing dwn …

don't say that!

if velocity is in the negative direction and "slowing down", then the velocity is increasing

the speed is getting less, but the velocity (measured in the positive "x" direction) is getting larger

don't think of velocity as if it was speed!

acceleration vs time graphs:

force = mass times acceleration, so the force always has the same sign as the acceleration

and of course, if the force is positive, it's to the right, and if it's negative, it's to the left

velocity vs time graphs:

the acceleration is always the slope (the tangent) of the velocity

does that help? :smile:
 
  • #6
thanx that helps a lot however... so if velocity is in the negative direction and slowing down you say that velocity is increasing. So if it is in the negative direction and speeding up it must be decreasing. If i am correct in that observation how is that so?
 
  • #7
yes you are correct in your observation.. see velocity is a vector so it going in -tve x direction means it has some -tve magnitude... then if you still accelerate in negative x then your velocity still gets more and more -tve magnitude...

Example : in the beginning it had v1=-5 (say) and after some time it has v2=-10... which among them is greater?
Hope you get it :smile:
 

Related to Velocity vs time and acceleration vs time

1. What is the difference between velocity vs time and acceleration vs time?

Velocity vs time is a graph that shows the relationship between the velocity of an object and the time it takes to travel. Acceleration vs time is a graph that shows the relationship between the acceleration of an object and the time it takes to change its velocity.

2. How are velocity and acceleration related in a velocity vs time and acceleration vs time graph?

In a velocity vs time graph, the slope of the line represents the acceleration. In an acceleration vs time graph, the slope of the line represents the change in acceleration over time.

3. What does a flat line on a velocity vs time graph mean?

A flat line on a velocity vs time graph means that the object is moving at a constant velocity, with no change in speed or direction.

4. How do you calculate acceleration from a velocity vs time graph?

To calculate acceleration from a velocity vs time graph, you can find the slope of the line or use the formula a = (vf-vi)/t, where vf is the final velocity, vi is the initial velocity, and t is the time interval.

5. What information can you gather from a velocity vs time and acceleration vs time graph?

A velocity vs time graph can show the speed and direction of an object at different points in time, while an acceleration vs time graph can show how the object's acceleration changes over time.

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