About projectile motion?

Question

Two balls are released simultaneously from a certain height.one ball is released freely while the other ball is projected horizontally(it falls making a parabolic shape)both these balls strike the ground at same time.
I think in the case of 2nd ball(moving in a parabolic shape)the distance has increased as compare to the 1st ball released freely but yet they strike the ground at same time.
why?

now if a fire a bullet horizontally from a certain height and at the same time i throw a bullet freely from my hand.
the 1st bullet will reach the ground making a curve(parabolic shape) will both the bullets still reach the ground at the same time.
i think no then how long the above application remains correct

Answer 1

go in space,
throw a ball horizontally: it will orbit.
let the ball fall freely: it will fall on the ground.

You're missing a very important notion: EARTH IS NOT FLAT !!!!
Honestly! you're an american, you should know! your country was discovered by someone who wanted to prove earth isn't flat... You should ALWAYS think about it!

IF earth was flat, and if the gravity field was the same everywhere (which is not the case), then both balls/bullets would hit the ground at the same time ONLY and only if you can neglect the lift a moving object might get from the atmosphere (like a paper plane: throw it horizontally, it will fly. Let it fall, it will go down... the diference comes from the presence of air on earth.)

now, what I'm saying is that you can only have your 2 balls touch the ground at the same instant if
- you can assume the lift won't affect your ball (don't throw it too hard)
- earth is locally flat (don't throw it too hard, and do your experiment in the salt lake area)

now you have those 2 prerequisites, you can begin the calculations, and you'll see (IF you neglet friction) that the horizontal velocity won't affect the vertical acceleration and velocity. If you don't neglet friction, you will have a difference between the 2 balls depending on what frictional model you use.


now, if you don't have these 2 prerequisites, then the balls you throw will have a good chance not to touch the ground at the same time.

If you throw the ball too hard, it might not even fall back on the ground, and might achieve escape velocity (might go in space)

Answer 2

Okay, the force applied on the second ball is horizontal, not vertical and as acceleration is proportional to force and the only force acting in vertical direction is the weight of the ball, the acceleration in the vertical direction for both the balls would be caused by its weight, not the force that has been exerted in any other direction. So, both the balls accelerate downwards at the same rate and so they hit the ground at the same time. The force exerted horizontally does not affect the vertical velocity of the second ball.

Answer 3

The acceleration of gravity is constant and always "points" straight down. Therefore any horizontal motion will not affect the time it takes for the ball to hit the ground even though it will travel a longer total distance.

Answer 4

The gravitational force on the balls is the same. It does not matter whether one is moving or not. Gravity effects each ball the same.

In the case of the ball that was just dropped, there is one force acting on it, 9.8 m/s^2 down.

In the case of the second ball there are two forces acting on it. 9.8 m/s^2 down, and some horizontal force.

It does not matter what the horizontal force is because the vertical force is the same on each object.

Answer 5

Because you have added force to the ball that is projected horizontally.

Answer 6

Because everything falls, according to gravity, at -32ft./second SQUARED. In other words, the object is ACCELERATING THROUGHOUT the fall, so the second object is hitting the graound at a speed much faster than the first.