Вы находитесь на странице: 1из 2

# Physics Unit 5 Week 3 Discussion Conservation of Momentum Before You Begin!

1 kg

BEFORE

1 kg

AFTER ?

b.

According to the intuitive guess you just made, predict if the overall momentum of the two-cart system after the collision greater than, less than, or equal to the overall momentum before the collision? Calculate this out using the momentum formula you figured out above and plugging in the relevant numbers.

2.

In a similar experiment, the 1 kg cart collides with a 3 kg cart but doesnt stick to it. Instead, the 3 kg cart gets knocked forward by the 1 kg cart which comes to rest after the collision.
6 m/s BEFORE

a.

Again, using intuition, predict the post-collision speed of the 3 kg cart. Briefly explain your reasoning.

1 kg

3 kg

AFTER

b.

According to the guess you just made, is the overall momentum of the two-cart system greater than, less than, or equal to the overall momentum before the collision. Calculate this out using the momentum formula you figured out above and plugging in the relevant numbers.

stopped

Part II: More Applications 3. SUV vs. Car On a test track, an SUV of mass 2000 kg, traveling at 12 m/s, hits a stationary car of mass 1000 kg. The car crumples and stays in contact with the SUV; they move together as a unit. a. Answer this without doing calculations: Predict which vehicle, if either, undergoes a greater change in velocity during the collision? How do you know?

b.

Without using formulas, see if you can intuitively guess the post-collision speed of the two vehicles. Briefly explain your common-sense reasoning.

c. 4.

## Calculate the post-collision speed using momentum.

Bowling Ball vs. Bowling Pin A bowling ball rolls into a stationary bowling pin, which is much lighter than the ball. a. During the collision, predict if the force exerted by the ball on the pin greater than, less than, or equal to the force exerted by the pin on the ball? Briefly explain.

b.

During the collision, predict if the bowling balls change in speed greater than, less than, or equal to the pins change in speed? Briefly explain.

c.

During the collision, predict if the bowling balls change in momentum greater than, less than, or equal to the pins change in momentum? Briefly explain.

d.

## A student makes the following argument about part C:

In the collision, the pins momentum changes more than the balls momentum, because the balls motion hardly changes, while the pins motion changes a lot; it bounces off the ball really fast.

How could you help this student reconcile his intuitive ideas about the changes in motion with the fact that the balls momentum and the pins momentum change by the same amount?
{"found_math": false, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0}