Question

A rock is thrown horizontally from a cliff at 25 m/s. What will its horizontal and vertical velocities be after 2.0 s?

Answer 1

Answer:

Explanation:horizontal: 25.0 m/s, vertical: -19.6 m/s

As the rock is thrown horizontally, it follows a parabolic motion (projectile motion), where:

- The horizontal motion is a uniform motion, with constant velocity

- The vertical motion is a uniformly accelerated motion, with constant acceleration  towards the ground (we take upward as positive direction, so the acceleration is negative)

We said that the horizontal velocity is constant, so it remains equal to the velocity at which the rock was thrown from the cliff, therefore

And this is also the value of the horizontal velocity at t = 2.0 s.

Instead, the vertical velocity follows the equation

where:

is the initial vertical velocity

is the acceleration of gravity

t = 2.0 s is the time

Substituting,