Lecture 17: Impulse - Rockets
recorded by: Massachusetts Institute of Technology, MIT
published: Oct. 10, 2008, recorded: October 1999, views: 4985
released under terms of: Creative Commons Attribution Non-Commercial Share Alike (CC-BY-NC-SA)
Download mit801f99_lewin_lec17_01.m4v (Video - generic video source 104.5 MB)
Download mit801f99_lewin_lec17_01.rm (Video - generic video source 106.0 MB)
Download mit801f99_lewin_lec17_01.flv (Video 105.3 MB)
Download mit801f99_lewin_lec17_01.wmv (Video 428.7 MB)
Report a problem or upload filesIf you have found a problem with this lecture or would like to send us extra material, articles, exercises, etc., please use our ticket system to describe your request and upload the data.
Enter your e-mail into the 'Cc' field, and we will keep you updated with your request's status.
1. Ballistic Pendulum:
A massive pendulum absorbs a bullet and the bullet's momentum. The kinetic energy which is left over after this completely inelastic collision is converted to potential energy of the pendulum. The relationship between horizontal displacement of the pendulum and bullet velocity is derived and empirically observed. The initial kinetic energy in the bullet is almost totally converted into heat.
2. Impulse and Impact Time:
Impulse is the product of a force (acting on an object) and the brief time that it acts. This results in an abrupt change of momentum. For a ball bouncing off the floor, the impact time is typically milliseconds. A movie is shown to demonstrate this. Courtesy of Dr. Peter Dourmashkin, MIT.
3. Surprising Bounce Demo:
A tennis ball on top of a much heavier basketball is dropped from a height of about 3 m. The tennis ball bounces way higher than 3 m. Try calculate how high it bounced by assuming the basketball bounces off the floor elastically and then collides elastically with the tennis ball.
4. Thrust of a Rocket:
An analogy is drawn between the force felt by the target of a tomato thrower, the reaction force felt by the thrower, and the propulsion (thrust) of a rocket. The Saturn rockets spewed out about 15 tons/sec at a speed of 2.5 km/sec relative to the rocket to provide a thrust of about 34 million Newton. The mass of the rocket decreases substantially with time as it burns its fuel, so the rocket's acceleration increases.
5. Fuel Consumption and Rocket Velocity:
Consuming a given amount of fuel translates into a fixed change of the rocket's momentum, not into a fixed change of the rocket's kinetic energy.
Link this pageWould you like to put a link to this lecture on your homepage?
Go ahead! Copy the HTML snippet !