Conservation of Momentum – EP – 2
5 Minutes
Conservation of momentum for students: learn how momentum is transferred and conserved in collisions and turns. A science lesson in English.
- Two hanging balls colliding to demonstrate momentum transfer
- How colliding balls lose energy as heat and sound
- Using weight shifting and barbell wheels to turn without slowing
What this lesson teaches
The law of conservation of momentum states that the total momentum of a system remains constant when no external forces act upon it. Momentum is a property an object gains when its mass is in motion, depending directly on both its mass and its speed.
Colliding balls experiment
When a hanging ball is lifted and released, it gains momentum and strikes a second ball of equal mass. The striking ball transfers its momentum to the second ball, causing it to swing upward. The second ball does not reach the original drop height because some of the initial momentum is converted into heat from friction and into sound energy during the collision. When there are no outside disturbances such as wind acting on the system, the overall momentum remains conserved.
Conditions for conservation
- An object with mass gains momentum whenever it is set in motion.
- When one object hits another, momentum moves from the striking object into the resting object.
- External forces, such as wind blowing along the path of motion, will disturb the system and change the final result.
- Total momentum stays constant only when the entire system is free from outside disturbances.
Shifting momentum during a turn
A moving vehicle forms a single system whose total momentum remains constant even when weight shifts between wheels. In a car with a mass of 40 kilograms, each of the four wheels carries 10 kilograms. If one side is lifted, the entire 40 kilograms shifts onto two wheels, giving each wheel 20 kilograms. Transferring this weight to the wheels on the outside of a turn increases their momentum while decreasing momentum on the inner wheels, allowing the vehicle to complete the turn smoothly without skidding or reducing speed.
Barbell wheel test
- Two barbells with balanced weights move forward easily in a straight line.
- Forcing the balanced barbells to turn normally requires them to slow down.
- Adding more weight to one side increases that side's momentum while lowering momentum on the opposite side.
- This uneven momentum allows the barbell system to turn automatically without losing speed.