How to describe characteristics a parabola?

[decadyne]

Help me understand the components of a parabola as created by a physical object in normal gravity.

The object has some forward velocity, some upward velocity, and at some point some downward velocity. Is this correct?

Is it safe to say, therefore, that at some point the parabola's vertical-axis velocity is zero? This is at the apex, correct?

Please tell me more about how to describe it, and if my assumptions are correct. Are there any other places where its characteristics can be predicted?

 

[Xezlec]

The parabola you seem to be discussing is the trajectory of a mass with some initial velocity in an environment with uniform gravity and no friction. The properties you have listed are correct. But when you say "the parabola's velocity", what you mean to say is either "the object's velocity" or "the parabola's derivative". A derivative is the mathematical property of a geometric shape that corresponds to the concept of velocity of the object in this case.

All of the characteristics of the parabolic trajectory can be predicted. Are there any in particular that you are curious about? In this case, the forward velocity is always the same (since there is no friction, and since gravity has no component in that direction and therefore no effect in that direction). The vertical velocity at every point in time can be computed using the definitions of force (F=dp/dt) and momentum (p=mv) and a little simple calculus, bearing in mind that "uniform gravity" means the gravitational force is always downward and always the same number. Specifically,

F = dp/dt = d(mv)/dt = m dv/dt.

Then, integrating both sides,

t F = m (v + v0).

So,

v = v0 + (t F / m),

where v is the upward velocity at time t, v0 is the upward velocity at time t=0, F is the force of gravity (which should be a negative number because it is downward), and m is the mass of the object. Since the force due to gravity on Earth is g m, where g=-9.8 m/s/s, we can be even more specific:

v = v0 + (t g m / m) = v0 + t g = v0 - 9.8 t,

Where v and v0 are in m/s and t is in seconds.

Does that about clear it up?

 

[sir-pinski]

A parabola is a symmetrical curve that is formed by the intersection of a plane and a right circular cone. It can also be described as the graph of a quadratic function, where the equation is in the form of y = ax^2 + bx + c. This means that the parabola has a specific shape and can be defined by its vertex, focus, and directrix.

The vertex is the point where the parabola changes direction and is located at the minimum or maximum point of the curve. In the case of an object in normal gravity, this would be the highest point of its trajectory. The focus is a fixed point located on the axis of symmetry, and the directrix is a straight line perpendicular to the axis of symmetry.

In terms of the object's motion, the parabola's characteristics can be described by its velocity, acceleration, and displacement. When the object is first launched, it has a forward velocity and an upward velocity. As it moves through the air, it experiences a downward acceleration due to gravity. This results in a parabolic path because the vertical velocity decreases until it reaches zero at the apex, and then increases again as the object falls back to the ground.

It is correct to say that the parabola's vertical-axis velocity is zero at the apex, as this is the point where the object's vertical velocity changes from positive to negative. This is also the point where the object's acceleration changes from negative to positive.

Other characteristics of a parabola that can be predicted include the axis of symmetry, which is a vertical line passing through the vertex, and the x-intercepts, which are the points where the parabola intersects with the x-axis. The y-intercept can also be predicted, as it is the point where the parabola intersects with the y-axis.

In summary, a parabola can be described by its shape, vertex, focus, directrix, and other characteristics such as velocity, acceleration, and displacement. Understanding these components can help you visualize and predict the path of an object in normal gravity.