Question

An object is thrown horizontally off a cliff with an initial velocity of 5.0 meters per second. The object strikes the ground 3.0 seconds later. What is the vertical speed of the object as it reaches the ground? [Neglect friction.]

Answer 1

The acceleration of gravity is 9.8 m/s².  This simply means that when anything falls, its downward speed keeps increasing, and it falls 9.8 m/s faster every second than it fell 1 second earlier.

After 3 seconds of falling, the object is falling at (3 x 9.8 m/s) = 29.4 m/s faster than at the beginning of the 3 seconds.  If it had no vertical speed at the beginning of the 3 seconds, then THAT's its speed after 3 seconds . . . . . 29.4 m/s downward.

As far as being thrown horizontally off the cliff . . . that has no effect on it vertical speed.  Horizontally, it doesn't matter whether it rolls gently over the edge, or somebody throws it horizontally, or it gets shot horizontally out of a high power rifle.  It hits the ground at the same time and with the same speed in every case.

Answer 2

The vertical speed of the object as it reaches the ground is about 29 m/s

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Further explanation

Acceleration is rate of change of velocity.

$\large {\boxed {a = \frac{v - u}{t} } }$

$\large {\boxed {d = \frac{v + u}{2}~t } }$

a = acceleration (m / s²)v = final velocity (m / s)

u = initial velocity (m / s)

t = time taken (s)

d = distance (m)

Let us now tackle the problem!

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Given:

initial horizontal speed of the object = u_x = 5.0 m/s

initial vertical speed of the object = u_y = 0 m/s

elapsed time = t = 3.0 s

Unknown:

final vertical speed of the object = v_y = ?

Solution:

The motion of the object is a parabolic motion.

We can use the following formula to calculate the vertical speed of the object as it reaches the ground:

$v_y = u_y + gt$

$v_y = 0 + 9.8( 3.0 )$

$v_y = 29.4 \texttt{ m/s}$

$v_y \approx 29 \texttt{ m/s}$

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Learn more

• Velocity of Runner : brainly.com/question/3813437

• Kinetic Energy : brainly.com/question/692781

• Acceleration : brainly.com/question/2283922

• The Speed of Car : brainly.com/question/568302

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Answer details

Grade: High School

Subject: Physics

Chapter: Kinematics