Projectile Motion

Table of Contents

Definition

  • A projectile is a particle moving near the Earth’s surface under the influence of its weight only (directed downward).
  • Horizontal velocity is constant.
  • Vertical velocity just like free fall.

Horizontal Projection

Displacement Calculation

  • For any constant acceleration: \(d = v_0t + \frac{1}{2}at^2\)
  • For any special case of horizontal projection:
\begin{equation*} \begin{split} a_x = 0; \\ a_y = g; \\ v_{0y} = 0; \\ v_{0x} = v_0 \end{split} \end{equation*}
  • Horizontal displacement: \(d_x = v_{0x}t\)
  • Vertical displacement: \(d_y = \frac{1}{2}gt^2\)

Velocity Calculation

  • For any constant acceleration: \(v_f = v_0 + at\)
  • For any special case of horizontal projection:
\begin{equation*} \begin{split} a_x = 0; \\ a_y = g; \\ v_{0y} = 0; \\ v_{0x} = v_0 \end{split} \end{equation*}
  • Horizontal displacement: \(v_x = v_{0x}\)
  • Vertical displacement: \(v_y = gt\)

General Projection

Displacement Calculation

  • The components of displacement at time \(t\) are:
\begin{equation*} \begin{split} d_x = v_{0x}t + \frac{1}{2}a_xt^2 \\ d_y = v_{0y}t + \frac{1}{2}a_yt^2 \end{split} \end{equation*}
  • For projectiles:
\begin{equation*} \begin{split} a_x & = 0; \\ a_y & = g; \\ v_{0y} & = v_0 sin\theta; \\ v_{0x} & = v_0 cos\theta \end{split} \end{equation*}
  • displacement components x and y for projectiles are:
\begin{equation*} \begin{split} d_x & = v_{0x}t \\ d_y & = v_{0y}t + \frac{1}{2}gt^2 \end{split} \end{equation*}

Velocity Calculation

  • The components of velocity at time \(t\) are:
\begin{equation*} \begin{split} v_x = v_{0x} + a_xt \\ v_y = v_{0x} + a_yt \end{split} \end{equation*}
  • For projectiles:
\begin{equation*} \begin{split} a_x & = 0; \\ a_y & = g; \\ v_{0y} & = v_0 sin\theta; \\ v_{0x} & = v_0 cos\theta \end{split} \end{equation*}
  • displacement components x and y for projectiles are:
\begin{equation*} \begin{split} v_x & = v_{0x}\ constant \\ v_y & = v_{0y} + gt \end{split} \end{equation*}

Summary

  Horizontal Vertical
Acceleration \(a_x = 0\) \(a_y = g\)
Velocity \(v_{ox} = v_0 cos\theta\) \(v_{0y} = v_0sin\theta\)
  \(v_x = v_{0x}\) \(v_y = v_{0y} + gt\)
Displacement \(d_x = v_xt\) \(d_y = v_{0y}t + \frac{1}{2}gt^2\)
    \(2gd_y = g_y^2 - (v_{0y})^2\)

Uniform Circular Motion

  • Uniform circular motion is motion along a circular path in which there is no change in speed, only a change in direction.
  • Velocity tangent to path.
  • Force toward center.

Centripetal Force

  • It is the force that keeps the object in circular motion.

Centripetal Acceleration

\begin{equation*} \begin{split} a_c & = \frac{v^2}{R}; \\ F_c & = ma_c = \frac{mv^2}{R} \end{split} \end{equation*}
  • where \(m\) is mass of the object, \(v\) is velocity, and \(R\) is radius of the circular path.
  • acceleration directed toward the center of circular path.

Tangential Velocity

  • when an object moves in a circular path at a distance \(r\) from the center, then the body's velocity is directed tangentially at any instant.
  • the linear velocity is its tangential velocity at any instant.

Tangential Acceleration

  • The rate of change of the tangential velocity of a particular in a circular orbit.

Formula (tho its not in the LAS): \(a_t = ar\)

  • \(a_t\) is the tangential acceleration, \(r\) is the radius of the circular path, and \(a\) is the angular acceleration.
  • always directs towards the tangent to the path of the body.

References

Date: August 17, 2023

Author: Paul Gerald D. Pare

Emacs 29.1 (Org mode 9.6.6)