General Mathematics Paper 2,Nov/Dec. 2014

Questions:	1	2	3	4	5	6	7	8	9	10	11	12	13	Main

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Weakness/Remedies
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Question 9

An object was thrown vertically upwards from the top of a cliff and its height, y metres, above sea level after t seconds is given by y = -16t2 + 64t + 5.

Copy and complete the table of values for y = -16t2 + 64t + 5; 0≤ t ≤ 4.0.

t	0.0	0.5	1.0	1.5	2.0	2.5	3.0	3.5	4.0
y	5			65			53

Using scales of 2 cm to 0.5 seconds on the t-axis and 2 cm to 10 m on the y-axis, draw the graph of y = -16t2 + 64t + 5 for 0 ≤ t ≤ 4.0.
Use the graph to find the
height reached when t = 1.75 seconds;
times the object was at a height of 50 m.
maximum height reached.

Observation

The Chief Examiner reported that this question was popular among the candidates and they performed very well in it. Majority of them were reported to have completed the table of values and plotted the points correctly. However, some of them did not apply the correct scale and some others could not read from the graph correctly. Candidates were expected to substitute each value of t into the equation to obtain the corresponding values for y and tabulate these values to obtain

t	0.0	0.5	1.0	1.5	2.0	2.5	3.0	3.5	4.0
y	5	33	53	65	69	65	53	33	5

Using these values of t and the given scales, candidates were expected to draw the graph as shown

From the graph, the height reached when t = 1.75 was 68 (± 0.5) m, the times the object was at a height of 50 m was 0.9 and 3.1 seconds (± 0.5 second) and the maximum height reached was 69 m.