Momentum — Science definition
The 'quantity of motion' of an object, p = mv; a vector measured in kilogram-metres per second (kg·m/s).
Where it is taught
- Momentum & Collisions — Work, Energy & Momentum, Physics & Environmental Science, Grade 12
In use
Momentum is an object's 'quantity of motion,' defined simply as p = mv — mass times velocity.
Momentum & Collisions
Questions using momentum
Problem 1
Find the momentum of a 0.50 kg ball moving at 4.0 m/s.
Answer and explanation
2 kg·m/s
p = mv = 0.50 × 4.0 = 2.0 kg·m/s.
Problem 2
Explain the following claim and supply a valid example or counterexample: Momentum conservation does not automatically imply kinetic-energy conservation.
Answer and explanation
Initialp=6 kg·m/s, totalm=3 kg, so vf=2 m/s with negligible external impulse. Momentum conservation does not automatically imply kinetic-energy conservation.
Response criteria
- State a scientifically accurate conclusion.
- Show the calculation or mechanism that supports it.
- Include units, conditions, or limits where relevant.
Problem 3
Find the momentum of a 6.0 kg object moving at 3.0 m/s.
Answer and explanation
18 kg·m/s
p = mv = 6.0 × 3.0 = 18 kg·m/s.
Problem 4
Find the momentum of a 0.20 kg ball moving at 30 m/s.
Answer and explanation
6 kg·m/s
p = mv = 0.20 × 30 = 6.0 kg·m/s.