What is Velocity at t=5s? Answer with Units

[NukeNuke]

Homework Statement

Tell me precisely what the velocity is when the time t = 5 seconds. include the appropriate units in your answer

the picture of the problem is here click the link then zoom into see the actual queston
http://img372.imageshack.us/img372/7473/43121337ma9.th.jpg

Homework Equations

The Attempt at a Solution

I tried adding the full distance divded by 5 but the answers wrong, i aslo tried subtracting the distance then divding by the time still wrong

then i assumed that it was just the distance by it self 200 divded by 5 but that's all wrong

 

[LowlyPion]

Homework Statement

Tell me precisely what the velocity is when the time t = 5 seconds. include the appropriate units in your answer

The Attempt at a Solution

I tried adding the full distance divded by 5 but the answers wrong, i aslo tried subtracting the distance then divding by the time still wrong

then i assumed that it was just the distance by it self 200 divded by 5 but that's all wrong

Velocity is the instantaneous rate of change of distance at a particular time.

That would be given on you graph by the slope of the line at the time asked.

Figure the slope at t=5.

 

[NukeNuke]

Velocity is the instantaneous rate of change of distance at a particular time.

That would be given on you graph by the slope of the line at the time asked.

Figure the slope at t=5.

okay so its 200 then what?

should i divide 200 by 5 or multiply it by 5 I am lost at this point

 

[LowlyPion]

okay so its 200 then what?

should i divide 200 by 5 or multiply it by 5 I am lost at this point

What is the slope of the graph at 5?

Not the value at 5 ... the slope.

How much does it CHANGE between 4 and 6 ?

 

[NukeNuke]

What is the slope of the graph at 5?

Not the value at 5 ... the slope.

How much does it CHANGE between 4 and 6 ?

it changes 200 that's the difference

 

[LowlyPion]

This must be were I am lost at cause i have no idea what I am looking for,

The final position for your purpose at 6 is what?
The initial position at 4 is what?

The rate of change of position is Final Position less Initial Position divided by the time to change position. So figure the time difference and divide the change in position. That is your velocity. That is also the slope of the graph at all points between 4 and 6 and hence that is the velocity at all times between 4 and 6 seconds.

 

[LowlyPion]

it changes 200 that's the difference

Not exactly. It changes (-200).

And the time is what? 2 seconds?

That means that Velocity is -200m/2s = -100 m/s

 

[NukeNuke]

O..okay thanks for the help