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.