Posted by **Melinda** on Sunday, December 4, 2011 at 2:12pm.

Someone verify if this is correct, please!

1. Draw a distance versus time graph that corresponds to the walk described below.

Adam starts 8 m away from the motion sensor and walks in a straight line toward the sensor at a constant rate of 0.5 m/s for 3 s. He immediately begins walking away from the sensor at a constant rate of 0.25 m/s for 4s. He stops for 1s and then walks toward the sensor at a constant rate of 0.5 m/s for 2 s.

Image is here imgur dot com/aKwAy

-----------------------------------

2.

During what interval of time was the greatest distance travelled?

a) 0<t<5

b) 5<t<7

c) 7<t<10

d) cannot be determined

I don't which one is correct, 0<t<5 or 5<t<7

here is the image:

imgur dot com/vOojV

Thank yhou~

- Math -
**MathMate**, Sunday, December 4, 2011 at 2:32pm
For (1), the x-coordinates are plotted correctly. You will need to review the y-coordinates, because they do not seem to correspond with the ones given in the question.

The starting point of 8 m is correct.

Walking towards the sensor makes a line with negative slope is correct also.

The rate is 0.5m/sec., so over 3 seconds, he would have been closer by 3*0.5=1.5m.

So at the end of 3 seconds, he would be at a distance of 8-1.5=6.5 m from the sensor.

Proceed this way for the rest of the question and see if you arrive at 6.5 m at the end of the 10 seconds.

(2) You'd need to interpret the graph where the y-axis represents speed given by m/s.

Interval, speed

0-5 3m/s

5-7 4m/s

7-10 1m/s

Since distance = speed * time, you can calculate the distance covered in each interval and the interval with the greatest distance travelled is the right answer.

- Math -
**Melinda**, Monday, December 5, 2011 at 12:29am
Got it! THank you~~~~~~~

- Math :) -
**MathMate**, Monday, December 5, 2011 at 3:32pm
Great! You're welcome!

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