1. Momentum and Impulse

2. Momentum is moving inertia
Momentum is an objects tendency to keep the motion it has.
 = mv
Momentum is always conserved in collisions.
The law of conservation of momentum states: the total momentum before a collision must equal the total momentum after the collision.

3. Momentum Practice Which has more momentum?
A 72 kg pig or a 2 kg jackrabbit?
The pig is walking at 0.5 m/s and the rabbit is hopping at a speed of 18 m/s.
Show K-U-E-S as part of your notes for this chunk.
After momentum problems as class….before impulse
Try as starter…hwk check

4. Impulse Impulse measures the intensity of an impact. Ft = f -I
Impulse is measured in Ns.
The longer the period of time it takes to apply the force, the less intense the force. Think a seat belt or crumple zone on a car or falling on a pillow.
The shorter the period of time it takes to apply the force, the more intense the force. Think of running into a brick wall on a bike or falling on the concrete.

5. Impulse Problems
A 72 kg pig is running with a momentum of 216 kg m/s. It then runs through some mud for 1.5 s. After running through the mud its momentum is 58 kg m/s. How much net force did the pig experience while running through the mud?
A 2 kg jackrabbit is running with a velocity of 18 m/s. It experiences about 200 N of net force when it runs into some briars and gets stuck. How much impulse did the jackrabbit experience while getting stuck?
Pig: N
Rabbit: -36 kgm/s optional t = 0.18 s

6. What was the independent variable in the bungee jumping activity?
Net force on the jumper
Time it takes to stop the jumper
Impulse of the jumper’s stop
Use this as the dq on schoology

7. Collisions
Elastic collisions: 2 objects collide and bounce off of each other.
m1v1 + m2v2 = m1v1 + m2v2
Before the collision After the collision
Inelastic collisions: 2 objects collide and stick together and continue moving.
m1v1 + m2v2 = (m1+ m2)v
Before the collision After the collision

8. Let’s try some calculations
Which equation should we use?
m1v1 + m2v2 = m1v1 + m2v2
Before
m1=
m2=
v1=
v2=
1000 kg
1000 kg(10 m/s) kg(2 m/s) =
1000 kg(v1) kg(4 m/s)
2000 kg
10 m/s
2 m/s
10000 kgm/s kgm/s =
1000 kg(v1) kgm/s
After
m1=
m2=
v1=
v2=
14000 kgm/s
- 8000kgm/s
- 8000kgm/s
1000 kg
1000 kg
6000 kgm/s
2000 kg
? m/s
= 6m/s
=v1
1000 kg
4 m/s