Momentum
Newton's Apple : Video Clip
 Momentum: is the inertia of motion
Momentum = mass x velocity
momentum = mv = P
 Impulse equals change in momentum
 The greater the force that acts on an object, the greater
will be the change in velocity, and hence, the change in
momentum.
 A long sustained force produces more change in
momentum than the same force applied briefly.
 Impulse: force x time (N * s)
 Impulse = change in momentum
 Case 1: increasing momentum
To increase momentum of an object, apply the greatest
force you can and extend the time of contact as much as
possible.
 Case 2: Decreasing momentum over a long time
If you want the force of impact to be small, extend the
time of impact.
Ex. Bending knees when you jump off something to the
ground below.
 Case 3: Decreasing momentum over a short time.
Making the time of contact very brief makes the force of
impact huge.
Ex. A karate expert breaking bricks.
 Bouncing: impulses are greater when bouncing takes
place.
 Law of Conservation of momentum:
In the absence of an external force, the momentum of a
system remains unchanged.
 Collisions
 Elastic collisions: momentum is transferred. Objects
are not permanently deformed and don’t generate heat.
 Inelastic collisions: objects become distorted and
generate heat; objects become tangled or couple
together.
P96 fig 7-14. Answers questions 1-3.
YouTube - Newton's cradle - Newtonin kehto
YouTube - Spectacular 1913 Train Collision
YouTube - inelastic collision
 Momentum vectors
Momentum is conserved even when colliding object move
at an angle to each other. P98 fig 7-15.
 Classwork answer questions p99 #1-20
Momentum