Lesson · P.3.2

Momentum and impulse

Momentum, p = m × v, and impulse, F × t = m × (v_f - v_i), the push behind a stop or a collision, plus conservation of momentum, which keeps the total steady when two objects collide, the way the HESI A2 physics subtest tests motion transferred between them.

ObjectiveP.3.2Read4 minExam weightEnergy and Momentum ≈ 20% of Physics

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What you will be able to do

You can calculate an object's momentum from its mass and velocity.
You can apply the impulse-momentum theorem to find a force, a time, or a change in velocity.
You can use conservation of momentum to find an unknown speed after two objects collide.

What the lesson concludes

Momentum is p = m × v, a vector that points the same way as the object's velocity.
Impulse is a force acting over time, impulse = F × t, and it equals the change in momentum it causes: impulse = m × (v_f - v_i).
The same change in momentum needs less force when it happens over more time, which is why easing a fall is safer than stopping it instantly.
In a closed system, total momentum right before a collision equals total momentum right after it.
When two colliding objects stick together, one combined mass carries the momentum both objects carried on their own.