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UNIT 4_LESSON 1 - MOMENTUM AND IMPULSE (1)

Momentum and Impulse

Lesson Objectives

  • Describe momentum and impulse.

  • Relate impulse and momentum to the collision of objects (e.g., vehicular collision).

  • Solve problems relating to momentum and collision.

  • Use concepts of impulse and momentum to appreciate vehicle safety features.

Mighty A vs Little B

  • Situation 1: Mighty A carries a huge rock to break the treasure's glass. Little B uses a marble to roll towards the treasure.

  • Guessing Game

    1. Which has a greater mass? (Huge Rock)

    2. Which breaks the glass first? (Mighty A)

    3. Who gets the treasure first? (Mighty A)

Things to Consider in Defining Momentum

  • Two main factors: a. The object has mass. b. The object is in motion.

  • Definition: Momentum means mass in motion. It describes the resistance of an object to stopping, defined mathematically as:

Mathematical Expression of Momentum

  • Formula:p = m * v

    • p = momentum (kg·m/s)

    • m = mass (kg)

    • v = velocity (m/s)

Comparing Momentum

  • Mighty A's rock has a greater momentum due to greater mass.

  • Little B's shot from the gun has a high momentum due to increased velocity.

  • Remember: MVP or MV = P.

Vector or Scalar

  • Momentum is a vector quantity; its direction aligns with velocity.

Problem Solving

  • Sample Problem 1:

    • Given mass (m) = 22 kg, velocity (v) = 1.2 m/s.

    • Momentum (p) = ?

    • Solution:p = m * v = 22 kg * 1.2 m/s = 26.4 kg·m/s

  • Sample Problem 2:

    • Given mass (m) = 300 kg, velocity (v) = 80 km/h (22.22 m/s).

    • Solution:p = m * v = 300 kg * 22.22 m/s = 6666 kg·m/s

Change in Momentum and Impulse

  • The greater the momentum, the greater the force needed to stop it.

  • An object at rest has zero momentum since its velocity is zero.

  • Impulse: Change in momentum due to collisions.

Impulse-Momentum Theorem

  • Formula: I = Δp = F * t

  • SI Unit for impulse (I) is Newton-second (Ns).

Sample Problems on Impulse

  • Offensive player passes a football:

    • Mass = 0.42 kg, velocity = 25.0 m/s, time = 0.050 s.

    • Average force (F) exerted by player calculation.

    • Results in F = 210 kg·m/s².

Conservation of Momentum

  • Law: The total momentum before and after a collision in a closed system is equal.

  • Sample Problem 1: Collision analysis between a truck (4000 kg, 15 m/s) and a car (1200 kg, 18 m/s).

Types of Collisions

  1. Elastic Collision: Both momentum and kinetic energy are conserved (e.g., hard metal balls).

  2. Inelastic Collision: Kinetic energy after collision is less than before (e.g., clay).

Types of Collision Conclusions**

  • During collisions, momentum is conserved. Energy can convert to heat or cause deformation.

  • Both perfect elastic and inelastic collisions are discussed with differing kinetic energy values.

Practice Problem

  • A train collision scenario with different calculations on post-collision speed, total kinetic energy, and type of collision.