Okay, so I drew the grid (albeit somewhat messily):

If I understand correctly, when t = 8 s, v(t) = 7.5 ms

^{-1} (roughly). Therefore, displacement = v(t)*t = 7.5 x 8 = 60 m. The book reads "18 m (approx)".

As for the second displacement question, I found the area of the trapezoid between t = 10 s and t = 12 s by doing ((8+7.5)/2)*2 = 15.5 m. The book reads "14 m (approx)".

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EDIT: I had another look at the second question from my original post and found the correct answer. Well, half of it -- the answer for the total time taken wasn't in my textbook.

First, I found the velocity given the acceleration, which was 20 ms

^{-1}. Next, I used the equation

*v*^{2} = u^{2} + 2ad to find

*d*. However, in order to get the right answer, I had to use 4 as the value for

*a, *which was the acceleration at the start of the object's movement. Why, then, is the deceleration not included somewhere in the equation? One would assume that you would need to include it in order to find the total distance travelled, as the distance would decrease or increase depending on how quickly the objected stopped moving.

Also, I used to the equation

* t = (v-u)/a* to calculate

* t* during the deceleration stage. I got an answer of 8 and added it to 17 to get a total time of 25 s for the object's movement. Is this correct?