Question

Figure gives the speed-time graph of the motion of a car. What is the ratio of the distance travelled by the car during the last two seconds to the total distance travelled in seven seconds?

• A. $\frac{1}{9}$
• B. $\frac{2}{9}$
• C. $\frac{1}{3}$
• D. $\frac{4}{9}$

Answer 1

Answer: (B)

Distance travelled in the last two seconds is
$S=$ area of triangle $B D C=\frac{1}{2} \times 20 \times 2=20 m$
Total distance travelled in seven seconds is
$S'=$ area of triangle $O A E+$ area of rectangle $A B D E$
+ area of triangle $B D C$
$=\frac{1}{2} \times 20 \times 3+20 \times 2+\frac{1}{2} \times 20 \times 2=90 m$
$\therefore \frac{S}{S^{\prime}}=\frac{20 m }{90 m }=\frac{2}{9}$