Chapter 6: Momentum, Impulse and Collision

Learning Outcomes

• Define momentum and impulse, and state the impulse-momentum theorem.

• Apply the impulse-momentum theorem to estimate average forces during collisions.

• Distinguish between the units of force and momentum.

• State the Law of Conservation of Momentum and apply it to recoil problems.

• Express Newton's Second Law of Motion in terms of momentum.

• Define inelastic, perfectly inelastic, and elastic collisions.

• Apply conservation laws of momentum and energy to one-dimensional collisions.

Key Terms

• Momentum: Defined as the product of mass and velocity.

• Impulse: Change in momentum resulting from a force applied over time.

• Inelastic Collision: Momentum conserved but kinetic energy not conserved.

• Elastic Collision: Both momentum and kinetic energy are conserved.

Concepts

Momentum and Impulse

• Formula: p = mv (momentum), where p = momentum, m = mass, v = velocity.

• Impulse-Momentum Theorem: I = F * Δt = Δp (Impulse = Change in momentum)

• Units: SI unit for momentum is kg m/s.

Conservation of Momentum

• Law: Total momentum before collision = Total momentum after collision.

• Application: Useful for solving collision problems.

Types of Collisions

1. Inelastic Collision: Two objects collide and move together post-collision.

2. Perfectly Inelastic Collision: The most extreme case where momentum is conserved, but kinetic energy is not; the objects stick together.

3. Elastic Collision: Both momentum and kinetic energy are conserved. Objects rebound separately after the collision.

Example Problem

• A tennis ball of 57 g falling from -1.2 m/s to +1.2 m/s over 0.02 s. Average force can be calculated using the formula: F_avg = Δp / Δt.

Collision Questions

• Example Inquiry: If a car and truck collide with the truck having double the pre-collision velocity, question which experiences a larger change in momentum involves understanding relative velocities and mass differences.

Practice Exercises

• Calculate average forces, momentum changes, and analyze collisions using the principles and formulas discussed.

Subsequent Topics

Chapter 7: Rotational Motion and Gravitation

• Key concepts will cover torque, center of mass, rotational dynamics, and energy.

Chapter 8: Fluids and Solids

• Introduction to fluid mechanics, density, pressure, and buoyancy.