Speed

 

  Disregarding air resistance, what is the speed of a ball dropped from 12 feet just before it hits the ground?     

  (Use 1 ft = 0.30 m, and use g = 9.8 m/s2.)     

 

  S  =  (1/2) a t²     

 

  (12 ft) • (0.30 m/ft)  =  (1/2) • (9.8 m/sec²) • t²     

  3.6 m  =  (4.9 m/sec²) • t²     

  t²  =  (3.6 m) / (4.9 m/sec²)     

  t²  =  0.735 sec²     

  t¹  =  0.857 sec     

 

  V  =  a t     

  V  =  (9.8 m/sec²) • (0.857 sec)     

  V  =  8.34 m/sec     

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