O-LevelPhysicsKinematics5054/22 · Oct/Nov 2022 · Q17 Marks

A train travels along a straight horizontal track. At time t = 0, the train passes through station P at constant speed without stopping. The driver applies the brakes 70s before reaching station Q. The train decelerates. Fig. 1.1 is the speed-time graph for the train from t = 0 until it stops at station Q. [Figure 1.1]

(a)Using Fig. 1.1, determine the distance between station P and station Q.[3]
(b)(i)The mass of the train is 3.8 × 10⁵ kg. Determine the deceleration of the train in the 70s before it stops at station Q.[2]
(b)(ii)Calculate the resultant force on the train as it decelerates.[2]

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Mark scheme

Marking points from the official mark scheme (Oct/Nov 2022). The mark or mark type is shown in brackets.

[C1] (distance =) area (under graph) or 77 × 56 or ½ × 77 × 70 or 4300 or 2700 or ½ x 77 x (56 + 126)
[C1] 77 × 56 + (1/2 × 77 × 70) or 4300 + 2700 or ½ × 77 × (56 + 126)
[A1] 7000 m or 7.0 × 10³ m or 7.0 km
[C1] (a =) Δv / Δt or 77/70 (etc.)
[A1] 1.1 m/s²
[C1] (F =) ma or 3.8 × 10⁵ × 1.1
[A1] 4.2 x 10⁵ N

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