The diagram shows a velocity-time graph which models the motion of a car. The graph consists of six straight line segments. The car accelerates from rest to a speed of $$\(20 \mathrm{~m} \mathrm{~s}^{-1}\)$$ over a period of $$\(5 \mathrm{~s}\)$$, and then travels at this speed for a further $$\(20 \mathrm{~s}\)$$. The car then decelerates to a speed of $$\(6 \mathrm{~m} \mathrm{~s}^{-1}\)$$ over a period of $$\(5 \mathrm{~s}\)$$. This speed is maintained for a further $$\((T-30) \mathrm{s}\)$$. The car then accelerates again to a speed of $$\(20 \mathrm{~m} \mathrm{~s}^{-1}\)$$ over a period of $$\((50-T) \mathrm{s}\)$$, before decelerating to rest over a period of $$\(10 \mathrm{~s}\)$$. Given that during the two stages of the motion when the car is accelerating, the accelerations are equal, find the value of $$\(T\)$$. .................................................................................................................................................... .................................................................................................................................................... .................................................................................................................................................... .................................................................................................................................................... .................................................................................................................................................... ....................................................................................................................................................

Mathematics
IGCSE&ALevel
CAIE
Exam No:9709_w21_qp_42 Year:2021 Question No:1(a)

Answer:

\(\frac{20-6}{50-T}=\frac{20}{5}\) or \(20=6+\frac{20}{5(50-T)}\)
\(T=46.5\)

Knowledge points:

4.2.1 understand the concepts of distance and speed as scalar quantities, and of displacement, velocity and acceleration as vector quantities Restricted to motion in one dimension only. The term ‘deceleration’ may sometimes be used in the context of decreasing speed.

Solution:

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