A stone thrown horizontally from a height of 6.12 m hits the ground at a distance of 12.90 m. Calculate the initial speed of the stone. Neglect air resistance.

Question

anonymous · Answer

@pocahontas Which formula to use

anonymous · Answer

This is Physics, bro. Lucky for you, I know it. Give me a few seconds to write it out.

anonymous · Answer

Ok. Go on Youtube and enter this "Projectile Motion, Launched from a Known Height" The video will show you how to solve. Now remember, though it is solving for Dx. Just rearrage the formulas for Vo.

phi · Answer

I would figure out how long it takes for a stone to reach the ground if dropped from a height of  6.12 m.  I would use
Distance = 0.5 * g* t^2  where g is the acceleration due to gravity, t is the time in seconds,  and distance is the distance fallen (in meters)

The problem says the stone was thrown horizontally (not up or down).  That means it will fall down and reach the ground in the same time it takes if just dropped.

I would then use
Distance = speed*time
You know the horizontal distance is 12.90 meters
you know time from the first step.  Now use algebra to solve for the speed.