what does initial velocity mean and how do you calculate it?

Question

how do you calculate it given the maximum height, range, or anything? basically how do calculate it for a projectile launched at an angle? and what is it exactly?

ok to be a little more specific, how would you calculate the initial velocity of a ball kicked into the air? when it was originally on the ground.

Answer 1

initial velocity is the velocity when time = 0. For example, if you were throwing something the initial velocity would be the velocity of the projectile the moment it left your hand, before the force of gravity had a chance to act on it.

There are a lot of different equations defining the relations between the things you mentioned above, can you be a little more specific?

EDIT: to find the initial velocity of a ball kicked into the air there are several equations you can use.

if you know the height the ball reached you can use energy equations to find the initial velocity


Potential energy = mass*gravity (gravity on earth is 9.8 m/s/s)*height

Kinetic energy = (1/2)mass*velocity^2

the change in potential energy = the change in kinetic energy

So, in the case of the ball:
mgh=(1/2)mv^2
gh=(1/2)v^2

As you can see you don't need to know the mass of the ball to find the initial velocity it was kicked at.

Answer 2

Define Initial Velocity

Answer 3

There are many situations that call for knowing Vo.
Ex: If you're on the top of a cliff y meters high and you throw a rock down over the edge at Vo, and you need to know the velocity when it hits the ground
V^2 = Vo^2 + 2*g*y

You give it a head start at building velocity. The acceleration due to gravity would accelerate it if you just dropped it, but if you throw it down, the acceleration due to gravity would accelerate the rock on the way down giving it additional velocity on top of what you gave it.

Maybe your problem gave you the height of the cliff, the velocity the rock hit the ground with, and said that the rock was thrown down from the top. You could calculate the initial velocity Vo from the equation above.
V = velocity it hit the ground with.
Vo = initial velocity, the unknown in this case.
g = 9.8 m/s^2.
y = height of the cliff.

The initial velocity of a ball kicked into the air would in many cases be zero. But it could have previously been kicked by someone else, in which case it might have some initial velocity.