1. Unit 4: Momentum & Impulse
I can calculate momentum using p=mv
I can calculate impulse using I = Ft

2. Momentum Momentum = Mass in motion
Any object that is moving has momentum

3. vs
fast
Which is harder to stop?
Which is harder to stop?
slow

4. What is the equation for momentum?
Momentum depends on the mass of the object and the velocity at which its traveling
Momentum is DIRECTLY proportional to mass and velocity. (if mass , momentum , if velocity , momentum )
Momentum = mass x velocity
p = m x v

5. What are the units for momentum?
p = m x v
Momentum = mass x velocity
kg∙m/s = kg x m/s

6. What are the units for momentum?
Units = kg∙m/s
Measurement
Unit
Distance
Meters (m)
Time
Seconds (s)
Velocity
m/s
Acceleration
m/s2
Force
Newton (N) (kg∙m/s2)
Momentum
kg∙m/s or Ns

7. WHICH HAS MORE MOMENTUM?
Think, Pair, Share
WHICH HAS MORE MOMENTUM? OR

8. What if I tell you…. Mass of the bullet = 0.045 kg
Velocity of bullet = 3000 m/s
Mass of elephant= 1250 kg
Velocity of elephant= m/s

9. EQUAL!! And the winner is…. p = mv
pbullet = (.045 kg)(3000m/s) = 135 kg∙m/s
pelephant = (1250 kg)(.108 m/s) = 135 kg∙m/s
EQUAL!!

10. Work it Out Determine the momentum of … 60-kg halfback moving at 9 m/s
1000-kg car moving at 20 m/s.
40-kg freshman moving at 2 m/s.
A bicycle has a momentum of 24 kg•m/s. What momentum would the bicycle have if it had …
twice the mass and was moving at the same speed?
the same mass and was moving with twice the speed?
one-half the mass and was moving with twice the speed?
three times the mass and was moving with one-half the speed?
three times the mass and was moving with twice the speed?
540
20000 80 48 24 36

11. I = F ∙ t = ∆p impulse What is impulse?
Impulse is the change in an object’s momentum
I = F ∙ t = ∆p
impulse
*when mass stays the same

12. I = F ∙ t = m ∙ ∆v momentum impulse What is impulse?
Impulse is the change in an object’s momentum
I = F ∙ t = m ∙ ∆v
momentum
impulse
*when mass stays the same

13. What are the units for impulse?
Units = N∙s or kg∙m/s
Measurement
Unit
Distance
Meters (m)
Time
Seconds (s)
Velocity
m/s
Acceleration
m/s2
Force
Newton (N) (kg∙m/s2)
Momentum
Ns or kg∙m/s
Impulse
N∙s or kg∙m/s

14. Examples

15. Quick Checks How do you stop an object with momentum?
Is it harder to stop an object with more mass or less mass?
Compare the forces I would need to exert to stop a bowling ball and a tennis ball traveling at the same speed.
What happens when an unbalanced force acts on an object?
What is acceleration?

16. Quick Checks
How do you stop an object with momentum? Force over a period of time
Is it harder to stop an object with more mass or less mass? More mass
Compare the forces I would need to exert to stop a bowling ball and a tennis ball traveling at the same speed. More force on the bowling ball
What happens when an unbalanced force acts on an object? It accelerates
What is acceleration? Change in velocity

17. Quick Checks When an object’s velocity changes, so does its…
What is the name for a change in momentum?
What is the equation we use to represent impulse?
Give 2 examples of impulses.

18. Quick Checks When an object’s velocity changes, so does its… momentum
What is the name for a change in momentum? impulse
What is the equation we use to represent impulse? Ft or m∆v
Give 2 examples of impulses.

19. Practice
During batting practice, a 0.30-kg baseball is hit with a bat that exerts a force of 350 N on the ball. The ball left the bat at 80 m/s. If the incoming pitch was traveling at 60 m/s, how long did the ball stay in contact with the bat?
Solve and Explain how the problem above is an example of impulse. (*don’t forget about direction*)
Change in velocity is 140 m/s!

20. HW
Momentum and Impulse ws
Don’t forget Newton’s 3rd Law!