The graph shows the speed, v metres per second (m/s), of a car at time t seconds - OCR - GCSE Maths - Question 15 - 2017 - Paper 1
Question 15
The graph shows the speed, v metres per second (m/s), of a car at time t seconds.
(a) Find the speed of the car at t = 7.
(b) It is claimed that the car has accele... show full transcript
Worked Solution & Example Answer:The graph shows the speed, v metres per second (m/s), of a car at time t seconds - OCR - GCSE Maths - Question 15 - 2017 - Paper 1
Step 1
Find the speed of the car at t = 7.
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Answer
To find the speed at t = 7 seconds, locate the value of v on the graph at this time. It appears to be approximately 25 m/s.
Step 2
Does the graph support this claim? Show your reasoning.
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Answer
To check if the car accelerated from 0 to 60 miles per hour (mph), first convert 60 mph to metres per second:
Now, observe the graph. By the 10-second mark, the speed is around 28 m/s. Thus, the graph supports the claim as the speed exceeds 26.82 m/s in the given time period.
Step 3
Use the graph to estimate the acceleration at t = 7.
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Answer
The acceleration can be estimated by drawing a tangent line at t = 7 seconds and calculating the slope. The speed changes from approximately 20 m/s (at t = 6) to about 25 m/s (at t = 7), over 1 second. Therefore, the approximate acceleration is:
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Answer
Since the speed, v, is directly proportional to the square of the time, t, we express this relationship mathematically as:
v=kt2
where k is a proportionality constant.
Step 5
Make one comment to show that this statement is incorrect.
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Answer
The graph indicates that after 10 seconds, the speed is leveling off, suggesting that the car will not continue to accelerate indefinitely. Therefore, Georgina's statement is incorrect.