Momentum

Summary and Exam Tips for Momentum

Momentum is a subtopic of Motion, Forces, and Energy, which falls under the subject Science in the IB MYP curriculum. Momentum is defined as the product of an object's mass and velocity ($p = mv$). It is a vector quantity, meaning it has both magnitude and direction, and is measured in kilogram meter per second (kg m/s) or newton second (N s). The principle of conservation of momentum states that in a closed system with no external forces, the total momentum before a collision is equal to the total momentum after the collision. This principle is crucial for solving problems involving collisions in one dimension. Impulse is the rate of change of momentum, calculated as the product of force and time ($\text{Impulse} = F \times t$). Increasing the time over which a collision occurs can reduce the force needed to change momentum, a concept applied in safety designs like airbags and crumple zones. Practical applications of momentum include playing billiards, where momentum is transferred between balls, and rocket propulsion, where expelling gas backward gives the rocket forward momentum.

Exam Tips

• Understand Key Equations: Be familiar with the equations for momentum ($p = mv$) and impulse ($\text{Impulse} = F \times t$). Practice using these equations in different scenarios.

• Conservation of Momentum: Remember that momentum is conserved in collisions. Practice problems involving collisions to understand how momentum is transferred between objects.

• Vector Nature of Momentum: Since momentum is a vector, pay attention to the direction of movement. Opposite directions can result in zero net momentum.

• Impulse and Safety: Understand how increasing collision time reduces force, as seen in airbags and crumple zones. This concept is often tested in practical application questions.

• Practice Problems: Solve a variety of practice questions to become comfortable with different types of momentum and impulse problems, including those involving changes in direction and velocity.