Physics
Impulse and the change in momentum
A force applied for a time changes momentum by that product. Rearranged, it gives the average force from a known change in momentum and contact time.
The Formula
J = F t = change in p
A force applied for a time changes momentum by that product. Rearranged, it gives the average force from a known change in momentum and contact time.
| Symbol | Meaning | Unit | Notes |
|---|---|---|---|
| F | Average force | newtons | Assumed constant over the contact time. |
| t | Contact time | seconds | How long the force acts. |
| dp | Change in momentum | kilogram metres per second | Final minus initial, so a rebound doubles it. |
What Each Symbol Means
Fnewtons
Average force
Assumed constant over the contact time.
tseconds
Contact time
How long the force acts.
dpkilogram metres per second
Change in momentum
Final minus initial, so a rebound doubles it.
See It Worked With Real Numbers
A formula on its own does not tell you which number goes where. The how to calculate momentum page applies this equation to a concrete case, shows every intermediate step, and names the mistakes that produce a wrong answer even when the algebra is right.
Where This Formula Appears
This equation is the working core of How To Calculate Momentum, filed under Science. Every number the guide produces comes from substituting into this one line.