Question

An object is thrown with a horizontal velocity of 20 m/s from a cliff that is 125 m above level ground. If air resistance is negligible, the time that it takes the object to fall to the ground from the cliff is most nearly

Answer 1

Given that,

Horizontal velocity of the object, v = 20 m/s

Height of the cliff, h = 125 m

We need to find the time that it takes the object to fall to the ground from the cliff is most nearly. It can be calculated using second equation of motion. Let us consider that the initial speed of the object is 0. So,

$h=ut+\dfrac{1}{2}at^2$

Here, a = g and u = 0

$h=\dfrac{1}{2}at^2\\\\t=\sqrt{\dfrac{2h}{g}} \\\\t=\sqrt{\dfrac{2\times 125}{10}} \\\\t=5\ s$

So, the object will take 5 seconds to fall to the ground from the cliff.