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YOUR PARTICIPATION FOR THE GROWTH OF PHYSICS REFERENCE BLOG

Saturday, October 28, 2017

The graph shows the vertical velocity of a parachutist during the first 20 s of her jump.






Question 1
The graph shows the vertical velocity of a parachutist during the first 20 s of her jump.


Approximately how far does she fall before opening the parachute?
A 390 m                      B 570 m                      C 710 m                      D 770 m





Reference: Past Exam Paper – November 2016 Paper 12 Q8





Solution:
Answer: B.
Opening the parachute causes a large decrease in velocity. From the graph, the approximate time at which the parachute is opened is t = 13s (the moment BEFORE the large deceleration).

Distance travelled = area under v-t graph. So, we need to find the area from t = 0s to t = 13s. This region can be approximated as follows:
Area of triangle from t=0 to t=5: distance = ½ × 5 × 44 = 110 m
Area of trapezium from t=5 to t=10: distance = ½ × (44+60) × 5 = 260 m
Area of rectangle from t=10 to t=13: distance = 60 × 3 = 180 m

Total distance travelled = 110 + 260 + 180 = 550 m
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