Free Fall in One Dimension

Example: A climber standing on the edge of a cliff throws a rock vertically downward. The initial velocity of the rock is 14\frac{m}{s}. If the rock reaches the ground 3 seconds later, how tall is the cliff?


Draw a picture:











  • v_{i}=14\ \frac{m}{s}
  • g=9.81\ \frac{m}{s}
  • t=3\ s
  • h_{f}=0\ m


  • h_{i}=?

Standard distance equationh_{f}=h_{i}+v_{i}t+\frac{1}{2}gt^{2}


Solve for h_{i}


(0\ m)-(-14\ \frac{m}{s})(3\ s)-(\frac{1}{2})(-9.81\ \frac{m}{s^2})(3\ s)^{2}=h_{i}

h_{i}=86.14\ m=height\ of\ the\ cliff