Momentum
p = mv
Warm-Up
Compare the force the big box exerts on the little box with the force the little box exerts on the big box.
Momentum
Momentum Song — The Hush Sound — Video SMTP
How Tough Is It to Stop?
"Which is tougher to stop, a bowling ball or a baseball?"
If the baseball had a much larger velocity, it would be harder to stop.
(technically, product of mass and velocity)
Defining Momentum
a) vector quantity
b) p has same direction as velocity
c) units - kg·m/s
Momentum and Collisions
Momentum helps us understand collisions
Kinetic Energy is conserved in perfectly elastic collisions
Same Momentum, Different Mass
"Could a moving baseball have the same momentum as a moving bowling ball?"
"Yes. p = mv. The baseball's velocity would have to be many times faster."
Force and Momentum
1) Relationship between force and momentum
Mathematical Relationship, F, p
What Determines the Change in Momentum?
The change in momentum that an unbalanced force produces on an object depends on ....
Follow Through Matters
"Could a female golfer EVER change the momentum of a golf ball more than a male golfer?"
2) Impulse
Combining all the equations
* J = Fnett = mΔv = Δp *
Write on your test immediately
before answering questions
Given this equation, what is another unit for momentum besides kg·m/s?
* J = Fnett = mΔv = Δp *
Explore: Impulse in a Crash
Same change in momentum, different stopping times.
Choose a speed and protection, then press Crash! The shaded area on the graph is the impulse.
Crash with no seat belt, then with a seat belt and airbag. Is the impulse the same? Is the force the same?
The impulse is the same (same mass and speed, so same Δp), but the longer stopping time makes the force much smaller.
NYSSLS Reading Passage · Dynamics
The Physics of the Fist: Force, Impulse, and the Evolution of the Boxing Glove
Open Reading Passage → Regents Practice Version →Check Your Understanding
5 quick questions — pick an answer to see if you’re right.
1. Which statement correctly describes momentum?
2. Besides kg·m/s, which unit can also be used for momentum?
3. What is the momentum of a 0.15 kg baseball moving at 40 m/s?
4. Can a moving baseball have the same momentum as a moving bowling ball?
5. How can a golfer who swings with less force still give a golf ball a larger change in momentum?
Designing a Phone Case
An engineering team is testing cases designed to protect a 0.20-kilogram cell phone. In each trial, the phone is dropped so that it strikes a tile floor at 4.0 meters per second and comes to rest without bouncing. A force sensor under the tile records how long the impact lasts. The results are shown in Table 1.
Diagram 1: Drop-Test Setup
Table 1: Drop-Test Results
| Case | Material | Impact Time (s) |
|---|---|---|
| A | No case | 0.0020 |
| B | Hard plastic | 0.0050 |
| C | Silicone gel | 0.016 |
Mass of phone and speed at impact are the same in every trial.
Which claim about Case C is best supported by the data in Table 1?
▶ Want a challenge? Open 6 more Regents-style questions (harder · mixed formats)
Challenge score: 0 / 6
C1. Substitute numerical values into a mathematical representation that can be used to determine the magnitude of the average force on the phone during the Case C impact. Then calculate the force.
C2. A student makes the following claim.
Place a check mark in either the Support or Refute box. Justify your response using a mathematical relationship.
C3. In a new trial with no case, the phone strikes the floor at 4.0 m/s downward and bounces straight up at 1.0 m/s. What is the magnitude of the impulse the floor exerts on the phone?
C4. Place a check mark in three boxes to indicate the quantities that must be known to determine the average force on the phone during an impact.
C5. During the Case B impact, choose the direction of the average net force on the phone, and determine its magnitude.
●
C6. The company plans to make Case C even thicker. Using evidence from Table 1, identify one benefit and one drawback of this design change.