# Falling stone!

• Jul 17th 2006, 11:03 PM
babygirl
Hello!
A stone is thrown horizontally with an initial speed of 7.5 m/s from the edge of a cliff. A stopwatch measures the stone's trajectory time from the top pf the cliff to the bottom to be 2.5 s. What is the height of the cliff?
• Jul 17th 2006, 11:20 PM
malaygoel
Quote:

Originally Posted by babygirl
A stone is thrown horizontally with an initial speed of 7.5 m/s from the edge of a cliff. A stopwatch measures the stone's trajectory time from the top pf the cliff to the bottom to be 2.5 s. What is the height of the cliff?

$h=\frac{1}{2}gt^2$
Solving, h=31.25m(g=10m/s^2)

Malay
• Jul 18th 2006, 07:28 AM
Soroban
Hello, babygirl!

Quote:

A stone is thrown horizontally with an initial speed of 7.5 m/s from the edge of a cliff.
This can be replaced with "A stone is dropped from the edge of a cliff."

A stopwatch measures the stone's trajectory time from the top of the cliff
. . to the bottom to be 2.5 s. .What is the height of the cliff?

A horizontal initial speed has no effect on the stone' descent.

Malay's solution is absolutely correct . . .