Momentum Semester Review

Impulse and Change in Momentum

Impulse equals a force multiplied by time and is equal to a change in momentum. \(J=Ft=\Delta p = m \Delta v\)

We have to remember that momentum is a vector when we are calculating the change in momentum. \(\Delta p = m \Delta v = m(V_f-V_i)\). If a 2kg ball bounces of a wall and changes velocity from 4 m/s to -2 m/s, for example, the change in momentum is -12kgm/s.

Impulse can be calculated by finding the area under a force time graph.

The slope of a momentum time graph is the net force exerted on an object.

Conservation of Momentum

If there is not a net force coming from outside the system then momentum is conserved. \(\Sigma p_i=\Sigma p_f \)

If momentum is conserved, the system is said to be a closed system because there are no net external forces.

The velocity of the center of mass does not change in a closed system that conserves momentum.

Types of Collisions

Momentum is always conserved between objects that collide.