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    4.  Three students  each hold a pendulum  of            the block aligns with the 8.5 cm mark, what is
                         identical length (50 cm) but with different bob      the actual length of the block?
                         weights: 50 g, 100 g, and 200 g. They each                                 (Pattern Recognition)
                         count 10 complete oscillations and record the
                         time as shown in the given table. All readings             (a)  8.5 cm         (b)  10.5 cm
                         are  nearly  identical.  Farida claims:  'Heavier
                         bobs swing faster — C should take the least                (c)  6.5 cm         (d)  6.0 cm
                         time.'
                                                                           6.  A pendulum is swinging in a room. If you pull
                                           Weights         Time
                                                                              the  "Bob"  slightly  further to  the  side  before
                         Student A           50 g          22.1 s             letting go, but do NOT change the length of
                         Student B          100 g          22.3 s             the string, what happens to the Time Period?
                         Student C          200 g         22.0 s                                    (Algorithmic Thinking)

                                                                                    (a)   The Time Period increases because
                                                                                       it has further to travel.

                                                                                    (b)   The Time Period decreases because
                                                                                       it moves faster.

                                                                                    (c)   The  Time Period  stays constant
                                                  50g
                                          100g
                                 200g                                                  because the length of the string has
                                                                                       not changed.
                         Why are all three time periods nearly equal,
                         and what does this tell us about what actually
                         controls a pendulum's time period?                         (d)   The pendulum will  stop  swinging
                                                                                       immediately.
                                                    (Decomposition)
                                                                           7.  The driver covered 40 km in 2 hours, resulting
                                (a)   Farida is correct  — heavier bobs       in an average speed of 20 km/h. Imagine the
                                   swing faster due to gravity pulling        driver stopped for a 30-minute coffee break
                                   harder.
                                                                              exactly at the halfway point, but still arrived
                                (b)   All are nearly equal because  the       at his destination in exactly 2 hours total. How
                                   time period of a pendulum depends          does  this break affect the overall  average
                                   on its length, not the mass of the         speed for the entire journey?
                                   bob  — all three pendulums  have                                 (Pattern Recognition)
                                   the same length.
                                                                                    (a)   The overall average speed
                                (c)   All are equal because the students               increases.
                                   made measurement errors.
                                                                                    (b)   The overall average speed

                                (d)   Time  period depends on the                      decreases.
                                   material of the bob — all three are              (c)   The overall average speed remains
                                   the same material.
                                                                                       the  same because  the  total time
                      5.  Rahul  is measuring  a wooden  block.  The                   (2 hours) is unchanged.
                         zero mark on his ruler is broken, so he starts
                         measuring from the 2 cm mark. If the end of               (d)  Average    speed    cannot    be
                                                                                       calculated if there is a break.

                                                                                   Measurement of Time and Motion     79

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