02.4b - Impulse

Momentum Resources:

- - Kognity Online Textbook - Use your ACS Login
  - IB Physics Site - Comprehensive Notes
  - IB Physics Net - Comprehensive Notes
  - Topic 2 Flashcards - Vocab Practice
  - Khan Academy - Momentum/Impulse
  - The Physics Classroom

Rocket Launch

For his Physics EE, Alejandro was testing two different lines of rocket engines. His goal was to optimize the the launch velocity of his 1.2 kg (total mass) model rocket. Within his EE on the stability of the center of pressure v. center of mass, it was essential that he be able to determine the maximum velocity of the rocket after the model engine finished burning. Once he had the data he wanted to verify that his data was accurate. The data he collected is to the right.

Create two different graphs to represent the data to the right.
Add a trendline with an equation to each graph.
Describe the importance/significance of the y-intercept of each trendline.
Describe the importance/significance of the slope of each trendline.
Based on the information provided (F, t, m, and Δv), does data fit for the size (mass) of model rocket Alé was using?

Please make a copy of the data HERE

Momentum and Impulse

Acceleration Defined

Cause of Acceleration

Show that:

This may seem like a complicated equation, however:

By applying a net force (F) for a period of time (t) onto (=) an object (m) the velocity will change (∆v).
To change the velocity (∆v) of an object (m), you must (=) apply a net force (F) for a certain period of time (t).
Follow through... In order to maximize the change in velocity (∆v) of an object, you should (=) increase the force (F) and/or the length of time (t) the force is applied.
Crashing/coming to a stop: When you crash (∆v) an object (m) you should (=) extend the time (t) to reduce the (F).

Using the Equation:

A hockey player applies an average force of 800.0 N to a 0.25 kg hockey puck for a time of 0.15 seconds.
1. Determine the impulse experienced by the hockey puck. ∆p = 120 Ns
2. What is the final velocity of the puck? ∆v = 40m/s

A 0.50-kg cart (#1) is pulled with a 1.0-N force for 1 second; another 0.50 kg cart (#2) is pulled with a 2.0 N-force for 0.50 seconds.
1. Which cart (#1 or #2) has the greatest acceleration? Explain. #2 F/m = 4m/s/s
2. Which cart (#1 or #2) has the greatest impulse? Explain. Both same
3. Which cart (#1 or #2) has the greatest change in momentum? Explain. Both same

Oh, Deer!!!
1. Jennifer, who has a mass of 50.0 kg, is driving at 35.0 m/s in her red sports car when she must suddenly slam on the brakes to avoid hitting a deer crossing the road. She strikes the air bag, that brings her body to a stop in 0.500 s. What average force does the seat belt exert on her? F = 3500N
2. If Jennifer had not been wearing her seat belt and not had an air bag, then the windshield would have stopped her head in 0.002 s. What average force would the windshield have exerted on her? F = 875000 N

Kinetic Energy & Momentum

There is a relation between kinetic energy and momentum as both the properties are linked with velocity. Momentum gets expressed as a multiplication of velocity and mass, whereas kinetic energy is the product of the square of speed and half of the mass.

A good mental exercise is to compare the concepts of energy and momentum using the following (and more) ideas:

Basic equation to describe concept (may be several for energy)
Units of concept
scalar/vector
Equation to change value
Kinetic energy equation in both concepts
Standard graphs of concepts, indicating important aspects of slope and area.

Energy / Momentum Comparison Question

While driving her new 1750-kg Ferrari 2021 812 Superfast/GTS, Becca accelerates from 100 km/hr (27.7 m/s) to 200 km/hr (55.5 m/s).

Using the equations for momentum and kinetic energy, describe the effect of doubling this velocity. The momentum doubles, the KE increase 4x.
The average breaking force of the carbon-ceramic brake rotors is 19800-N, describe the difference in the effect of doubling the velocity on the distance and time required to stop the 1750-kg car from 112 km/h (31.3 m/s). The time req'd doubles, while the distance increases 4x.

Momentum/Impulse Introductory Problems

Momentum / Impulse TSPs

Impulse - Momentum TSPs

Questions 1-9 are specific to using the impulse/momentum problem. Solutions can be found HERE.

2 - 2016_Topic_2_Problems_2.4.pdf

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