These are “plug-in-the-number” type activities to familiarize yon with the equations that link the concepts of physics. They are mainly one-step substitutions and are less challenging than the Problem. ? An object is dropped from rest and falls freely. After 7 s, calculate its instantaneous speed.

Solution 17PC The equation of motion that has to be used here is v = u + at. Given that, u = 0 m/s Acceleration a = g (for free fall) Acceleration, a = 9.8 m/s 2 Time t = 7 s Hence, instantaneous speed after 7 s is v = 0 m/s + 9.8 m/s × 7 s v = 0 m/s + 68.6 m/s v = 68.6 m/s Therefore, the object will have an instantaneous speed of 68.6 m/s.