Math Problem Statement

Derive the kinematic equations (1) vf = vi + at and (2) Δx = ((vf + vi)/2)t.

Solution

Let's begin by deriving the two kinematic equations shown in the image:

(1) Derivation of vf=vi+atv_f = v_i + at

This is a standard kinematic equation, where:

  • vfv_f is the final velocity,
  • viv_i is the initial velocity,
  • aa is the acceleration, and
  • tt is the time.

Step-by-step derivation:

  1. Definition of acceleration: Acceleration is defined as the rate of change of velocity. a=vfvita = \frac{v_f - v_i}{t}

  2. Rearranging for vfv_f: Multiply both sides by tt to isolate vfv_f. at=vfvia t = v_f - v_i

  3. Solving for vfv_f: vf=vi+atv_f = v_i + at

Thus, we derive: vf=vi+atv_f = v_i + at

(2) Derivation of Δx=(vf+vi2)t\Delta x = \left( \frac{v_f + v_i}{2} \right) t

This is another common kinematic equation, representing the displacement (Δx\Delta x).

Step-by-step derivation:

  1. Average velocity: The average velocity is defined as: vavg=vf+vi2v_{\text{avg}} = \frac{v_f + v_i}{2}

  2. Relationship between displacement and average velocity: Displacement is the product of average velocity and time: Δx=vavgt\Delta x = v_{\text{avg}} \cdot t

  3. Substitute the expression for average velocity: Δx=(vf+vi2)t\Delta x = \left( \frac{v_f + v_i}{2} \right) t

Thus, we derive: Δx=(vf+vi2)t\Delta x = \left( \frac{v_f + v_i}{2} \right) t


Would you like further details or have any questions? Here are five related questions that could deepen your understanding:

  1. How can these equations be applied to motion with constant acceleration?
  2. What would happen to these equations if the object was in free fall (where a=ga = g)?
  3. How do these equations change if the acceleration is zero?
  4. Can you derive a third kinematic equation that eliminates time from the expressions?
  5. How do we handle negative values for acceleration or velocity?

Tip: Always ensure units are consistent when solving kinematic problems (e.g., meters for distance, seconds for time).

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Math Problem Analysis

Mathematical Concepts

Kinematics
Linear Motion
Acceleration
Velocity
Displacement

Formulas

vf = vi + at
Δx = ((vf + vi)/2) * t

Theorems

Definition of Acceleration
Average Velocity Formula

Suitable Grade Level

Grades 9-12