A stone is dropped from the top of a cliff. It hits the ground after 55 s. How high is the cliff?

1 answer

To find the height of the cliff from which the stone is dropped, we can use the kinematic equation for an object in free fall. The equation is:

\[ h = \frac{1}{2} g t^2 \]

where:

  • \( h \) is the height (in meters),
  • \( g \) is the acceleration due to gravity (approximately \( 9.81 , \text{m/s}^2 \)),
  • \( t \) is the time (in seconds).

In this case, the stone is dropped, so \( t = 55 , \text{s} \).

Now, we can substitute the values into the equation:

\[ h = \frac{1}{2} \times 9.81 , \text{m/s}^2 \times (55 , \text{s})^2 \]

Calculating \( (55 , \text{s})^2 \):

\[ (55 , \text{s})^2 = 3025 , \text{s}^2 \]

Now substituting back into the height equation:

\[ h = \frac{1}{2} \times 9.81 , \text{m/s}^2 \times 3025 , \text{s}^2 \]

Calculating the multiplication:

\[ h = 0.5 \times 9.81 \times 3025 \]

Calculating \( 9.81 \times 3025 \):

\[ 9.81 \times 3025 = 29652.25 \]

Then multiplying by \( 0.5 \):

\[ h = 0.5 \times 29652.25 = 14826.125 , \text{m} \]

Thus, the height of the cliff is approximately:

\[ \boxed{14826.125 , \text{m}} \]