Impulse — Science definition
Defined in 2 courses:
- The product of force and the time it acts, J = FΔt; it equals the change in momentum, Δp. (Physics & Environmental Science)
- Time integral of force, equal to momentum change. (Physics & Environmental Science)
Where it is taught
- Momentum & Collisions — Work, Energy & Momentum, Physics & Environmental Science, Grade 12
- Impulse & Collision Evidence — Work, Energy & Momentum, Physics & Environmental Science, Grade 12
In use
To change an object's momentum you must apply a force for some time, and that combination is called impulse: J = FΔt.
Momentum & Collisions
Impulse J=∫Fdt changes momentum; for a known average force, J=FavgΔt=Δp.
Impulse & Collision Evidence
Questions using impulse
Problem 1
Answer and explanation
10 kg·m/s
Impulse equals the change in momentum: J = Δp = m(v_f − v_i) = 0.50 × (20 − 0) = 10 kg·m/s.
Problem 2
Answer and explanation
Initial momentum=12 kg·m/s, so vf=3 m/s. Ki=24 J and Kf=18 J;6 J leaves the kinetic category through other energy forms.
Initial momentum=12 kg·m/s, so vf=3 m/s.
Ki=24 J and Kf=18 J;6 J leaves the kinetic category through other energy forms.
Response criteria
- Use the stated measurements or conditions, with correct units.
- Connect the result to the physical or environmental mechanism or evidence relationship.
- Identify the assumption, model limit or further evidence requested.
Problem 3
Answer and explanation
Initial momentum=12 kg·m/s, so vf=3 m/s. Ki=24 J and Kf=18 J;6 J leaves the kinetic category through other energy forms.
Initial momentum=12 kg·m/s, so vf=3 m/s.
Ki=24 J and Kf=18 J;6 J leaves the kinetic category through other energy forms.
Response criteria
- Use the stated measurements or conditions, with correct units.
- Connect the result to the physical or environmental mechanism or evidence relationship.
- Identify the assumption, model limit or further evidence requested.
Problem 4
Answer and explanation
The passenger's change in momentum in the crash is fixed by their mass and speed. Since impulse FΔt equals that change in momentum, F = Δp/Δt. An airbag increases the stopping time Δt, and a larger Δt makes the average force F smaller, reducing injury.