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This lesson covers impulse and momentum at A-Level. Momentum is a fundamental concept in mechanics that is especially useful for analysing collisions and impacts. The principle of conservation of momentum is one of the most important laws in physics.
The momentum of an object is the product of its mass and velocity:
p=mv
| Property | Detail |
|---|---|
| Unit | kg m/s (or Ns) |
| Type | Vector (has direction) |
| Direction | Same as the velocity |
Exam Tip: Momentum is a vector quantity. Always define a positive direction and use signs consistently. A common error is to forget that velocity (and hence momentum) can be negative.
Impulse is the change in momentum of an object:
I=Δp=mv−mu
Impulse is also equal to force multiplied by time:
I=Ft(for a constant force)
More generally (for a variable force):
I=∫Fdt
The unit of impulse is Ns (newton-seconds) or equivalently kg m/s.
Ft=mv−mu
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