A car moves along a horizontal straight road, passing two points A and B - Edexcel - A-Level Maths Mechanics - Question 3 - 2008 - Paper 1
Question 3
A car moves along a horizontal straight road, passing two points A and B. At A the speed of the car is 15 m s^-1. When the driver passes A, he sees a warning sign W ... show full transcript
Worked Solution & Example Answer:A car moves along a horizontal straight road, passing two points A and B - Edexcel - A-Level Maths Mechanics - Question 3 - 2008 - Paper 1
Step 1
(a) Sketch, in the space below, a speed-time graph to illustrate the motion of the car as it moves from A to B.
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Answer
The speed-time graph can be divided into three segments:
Deceleration from A to W (0 to 12s): The speed decreases from 15 m/s to 5 m/s. This is a slope downwards.
Acceleration from W (12s to 16s): The speed increases from 5 m/s to V m/s. This is a slope upwards.
Constant speed (16s to 38s): The car moves with speed V m/s for 22 seconds, shown as a horizontal line.
The graph should form a 'V' shape. Ensure that each section is labeled appropriately.
Step 2
(b) Find the time taken for the car to move from A to B.
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Answer
The total distance covered is 1 km = 1000 m.
From A to W, the average speed is:
Average speed=215+5=10 m/s
Time taken from A to W:
t=10 m/s120extm=12exts
From W to the final point B, the car accelerates for 4 seconds (16 s - 12 s) and moves at constant speed for 22 seconds, totaling:
T=12+4+22=38 s
Step 3
(c) The distance from A to B is 1 km.
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Answer
Using the total distances covered:
The distance from A to W is 120 m and the distance covered while moving at V m/s over 22 seconds is given by:
D=V×t=V×22