A ball is dropped from the roof of a very tall building.What is its velocity after falling for 5.0s?
Correct answer: C. 49.0 m/s
- A. 1.96 m/s
- B. 9.80 m/s
- C. 49.0 m/s
- D. 98.0 m/s
Explanation
List the known and unknown values.u = initial velocity = 0 m/sv = final velocity = ?m/sa = g = acceleration due to gravity = 9.8 m/s²t = time interval = 5 ss = displacement = ? mCalculate the displacement using the following kinematic equation.s = ut + ½at²Since u = 0, the equation can be rewritten as:s = ½at²s = 0.5 × 9.8 m/s² × (5 s)² = 122.5 mCalculate the final velocity using the following kinematic equation.v = u + atv = 0 + (9.8 m/s² × 5 s) =49 m /s
This question appeared on the ETEA MDCAT 2014 paper, which you can sit online with every answer explained.
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Acceleration measures the rate at which velocity changes with time, including changes in speed, direction or both. Work includes average and instantaneous acceleration, the relation a = Δv/Δt, uniform acceleration equations, and interpreting velocity time and displacement time graphs, with acceleration carefully distinguished from velocity.
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