• Support PF! Buy your school textbooks, materials and every day products Here!

Velocity (avg/instantaneous)

  • Thread starter phragg
  • Start date
2
0
A position-time graph for a particle moving along the x-axis is shown below:

(a) Find the average velocity in the time interval t = 1.50 s to t = 4.00 s.
(b) Determine the instantaneous velocity at t = 2.00 s by measuring the slope of the tangent line shown in the graph.
(c) At what value of t is the velocity zero?


http://img241.imageshack.us/img241/1514/tangetsb6.jpg [Broken]

I figured that (a) was the easy part as I went ahead to solving that
[tex]v_{ave} = \frac{\Delta x}{\Delta t}[/tex]

[tex]\Delta t = t_f - t_i[/tex]
[tex]\Delta t = 4.00 s - 1.50s[/tex]
[tex]\Delta t = 2.50 s[/tex]

[tex]\Delta x = x_f - x_i[/tex]
[tex]\Delta x = 2m - 7m[/tex]
[tex]\Delta x = -5m[/tex]

[tex]v_{ave} = \frac{-5m}{2.50s}[/tex]
[tex]v_{ave} = -2m/s[/tex]

So after that was done I went on to part (b) which first asked to find the slope of the tangent point was easily done by:

[tex]m = \frac{y_2 - y_1}{x_2 - x_1}[/tex]
[tex]m = \frac{0 - 12}{4 - 0}[/tex]
[tex]m = \frac{-3}{1}[/tex]

Now I am completely stumped as to what they're asking for how to Determine the instantaneous Velocity at t = 2.00 s and Don't get me started on (c). Oh an p.s. Hey I'm new to PF ;p!
 
Last edited by a moderator:

CompuChip

Science Advisor
Homework Helper
4,284
47
Hi, welcome to PF.
Actually, you already solved b :)
The key thing you are missing, is that instantaneous velocity at some time is the slope of the (t, x) graph at that point.

This should also help you solve c.
 

Related Threads for: Velocity (avg/instantaneous)

Replies
3
Views
2K
  • Last Post
Replies
2
Views
3K
  • Last Post
Replies
7
Views
2K
  • Last Post
Replies
12
Views
3K
  • Last Post
Replies
2
Views
1K
  • Last Post
Replies
7
Views
3K
Replies
5
Views
2K
  • Last Post
Replies
4
Views
4K
Top