A heavy lorry crawling and a light bullet flying can carry the same punch. Momentum captures that combination of mass and velocity, and in any collision or explosion, when nothing pushes from outside, the total momentum is exactly the same before and after.
Momentum is mass times velocity: p = mv, measured in kg m/s. It is a vector, so direction matters. In a closed system with no external resultant force, the total momentum before an interaction equals the total momentum after it.
Momentum is mass multiplied by velocity. It is a vector quantity.
Conservation of momentum: with no external resultant force, the total momentum before an interaction equals the total momentum after.
Set the masses and velocities of two trolleys, then let them collide. Watch the readout: the individual momenta change, but the total momentum before the collision matches the total after.
Four quick checks on the definition, units, and conservation. Each correct answer earns XP and lights this skill on your star map.
Momentum is defined as...
The unit of momentum is...
Momentum is a vector quantity, which means...
In a closed system with no external resultant force, the total momentum...
A 3.0 kg trolley moving at 4.0 m/s collides with and sticks to a stationary 1.0 kg trolley. Find their common velocity after the collision.
Because momentum is a vector, you must include direction. A trolley moving left has a negative velocity if right is positive, so its momentum is negative. Adding momenta without checking their signs is the single most common error examiners see in Paper 4.
Unlocks once the four checks above are done. Worth more XP, written in the style of Paper 2.
A ball of mass 2.0 kg moves at 3.0 m/s. Its momentum is...
A 4.0 kg trolley moving at 3.0 m/s collides with and sticks to a stationary 2.0 kg trolley. Their common velocity afterwards is...
Two identical trolleys approach each other at the same speed and stick together on impact. Just after the collision they...
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