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A level question kinematics

  • Thread starter jh128273
  • Start date
4
0
1. Homework Statement
a car takes 3 mins to travel between 2 sets of traffic lights which are 1800m apart, its velocity at each set of lights is 0ms-1

If the car accelerated uniformly for 30 secs and then maintained a constant velocity for the next 2 mins before retarding uniformly, calculate the the maxumum uniform velocity reached.


2. Homework Equations

usual suvat

3. The Attempt at a Solution
 

Answers and Replies

648
2
Welcome to Physics Forums.
It's probably best done drawing a velocity time graph and using the fact that the area under the graph is the distance travelled.
Have you tried that?
 
4
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Thanks for the quick reply.

Yes I have looked at that but as I didnt have a velocity it seemed useless.

I think I'm struggling as there is only 2 components to use i.e. time and total distance.

I'll keep trying :)

cheers
 
648
2
The shape of the graph is a trapezium. If you know the formula for its area you have all you need to find the "height" of it. (Height= maximum velocity of car)
If you don't know the formula, treat the graph as 2 triangles and a rectangle and write down the area of each of those 3 shapes in term of the "height" of the graph.
Triangle area is half base times height. Rectangle is length times height.
 
4
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Yip, that done it...lol thanks alot for your help, it has cheers me up after a freak out earlier. I think I've been looking into further than was needed.

Thanks again,

Jeff
 

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