Study Notes
Momentum is the product of a body's mass and velocity, and it is a vector quantity. It is conserved in isolated systems during collisions.
- Momentum — The product of mass and velocity of a body. Example: A car with a mass of 1000 kg moving at 20 m/s has a momentum of 20,000 kgm/s.
- Conservation of Momentum — In an isolated system, the total momentum before a collision is equal to the total momentum after the collision. Example: Two ice skaters push off each other and move in opposite directions with equal and opposite momentum.
- Impulse — The change in momentum resulting from a force applied over a period of time. Example: A tennis racket hitting a ball applies an impulse to change the ball's momentum.
Exam Tips
Key Definitions to Remember
- Momentum is the product of mass and velocity.
- Conservation of momentum states that total momentum in an isolated system remains constant.
- Impulse is the change in momentum due to a force over time.
Common Confusions
- Confusing momentum with force; remember momentum is mass times velocity, not force.
- Forgetting that momentum is a vector and has direction.
Typical Exam Questions
- What is the momentum of a 5 kg object moving at 3 m/s? Answer: 15 kgm/s
- How does the momentum of a system change if no external forces act on it? Answer: It remains constant.
- Calculate the common speed of two colliding objects given their masses and initial velocities. Answer: Use conservation of momentum to find the final speed.
What Examiners Usually Test
- Understanding and application of the conservation of momentum.
- Ability to calculate changes in momentum and impulse.
- Solving problems involving collisions and determining final velocities.