Question
5. Mary sprints 200 m in 30 seconds, rests for 45 seconds and then walks back in 1(1)/(2) minutes to where she started the race. (a) Draw a distance-time graph for Mary. (b) Calculate the speed at which Mary runs. (c) Calculate the speed at which Mary walks.
Answer
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Terence
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Answer
(a) To draw a distance-time graph, plot the points (0,0), (30,200), (75,200), and (165,0). Connect the points with straight lines. (b) The speed at which Mary runs is
.(c) The speed at which Mary walks is
.
Explanation
## Step1: First, we need to calculate the time Mary takes to complete her journey in seconds. She sprints for 30 seconds, rests for 45 seconds, and walks back in
minutes which is equal to 90 seconds. ## Step2: To draw a distance-time graph, we plot the following points:- (0,0): Mary starts her sprint.- (30,200): Mary finishes her sprint after 30 seconds, covering 200 meters.- (75,200): Mary rests for 45 seconds (total of 75 seconds), her distance remains 200 meters.- (165,0): Mary walks back to the starting point after 90 seconds (total of 165 seconds), her distance becomes 0 meters.## Step3: To calculate the speed at which Mary runs, we use the formula:###
The distance Mary runs is 200 meters and the time taken is 30 seconds. ## Step4: To calculate the speed at which Mary walks, we use the same formula. The distance Mary walks is 200 meters (back to the starting point) and the time taken is 90 seconds.