Exam-style question
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A ball is thrown vertically upwards with an initial velocity of 20 m/s. Calculate the maximum height it reaches before falling back down. Assume acceleration due to gravity is -9.81 m/s².
Model answer
What a good answer should say
- The maximum height reached by the ball is 20.4 m.
Explanation
Why this works
This question tests the application of the equations of motion under constant acceleration. The formula used is v² = u² + 2as, where v is the final velocity (0 m/s at the maximum height), u is the initial velocity (20 m/s), a is the acceleration (-9.81 m/s²), and s is the maximum height.
Substituting the values gives: 0 = (20)² + 2(-9.81)s, solving for s yields 20.4 m.
Common mistake
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