Answer:
2.2 seconds
Explanation:
The attached graph shows the height of a rock after it falls from a cliff. Let after t seconds the rock is 20 meters from the ground.
If the graph is not given we can calculate the time using the second equation of motion i.e.
![d=ut+(1)/(2)at^2](https://img.qammunity.org/2020/formulas/physics/college/cnmnl56g8a1pmreipfvlacntz8hqzm02l7.png)
Where
u is the initial speed of the rock
a is the acceleration of the rock
t is the time taken
Here, distance covered is in y axis and the time taken is in x axis. Approximately, at 2.2 seconds the rock is 20 meters above the ground. Hence, this is the required solution.