This common misconceptions covers Common Misconceptions within Momentum for GCSE Physics. Revise Momentum in Forces for GCSE Physics with 13 exam-style questions and 6 flashcards. This is a high-frequency topic, so it is worth revising until the explanation feels precise and repeatable. It is section 7 of 12 in this topic. Use this common misconceptions to connect the idea to the wider topic before moving on to questions and flashcards.
Topic position
Section 7 of 12
Practice
13 questions
Recall
6 flashcards
⚠️ Common Misconceptions
Misconception 1: "Momentum is the same as force"
Momentum and force are completely different. Momentum is a property of a moving object (p = mv, units kg m/s). Force is what CHANGES momentum (F = Δp/Δt, units N). A large momentum does not require a large force to maintain — an object with huge momentum can coast with zero force if there's no friction (Newton's First Law). Force is needed to CHANGE momentum, not to maintain it.
Misconception 2: "In an explosion, the heavier piece has more momentum"
In an explosion from rest, total initial momentum = 0, so after the explosion the two pieces have equal and OPPOSITE momenta. The heavier piece moves more slowly; the lighter piece moves faster — but their momenta are equal in magnitude. A 10 kg piece at 6 m/s has the same momentum magnitude as a 6 kg piece at 10 m/s.
Misconception 3: "Kinetic energy is always conserved in collisions"
Only in perfectly elastic collisions is kinetic energy conserved. In most real collisions (cars crashing, balls of clay sticking together), some kinetic energy is converted to thermal energy and sound. Momentum, however, is ALWAYS conserved in a closed system regardless of collision type.