A Simple Model of a Rocket

1. A Simple Model of a Rocket

2. How it gets into the air • The engine produces thrust from burning of powder • The trust from the burning of the powder results in kinetic energy.

3. First … Thrust • Thrust is in Newtons for a giventime • To clarify use a simplified curve • 8 Newtons for 1.8 seconds • This is like a finger pushing the rocket into the air

4. Kinetic Energy and Work Done • Kinetic Energy • Work by a constant applied force: • So then the change in kinetic energy is: • The result is that the work done by the rocket engine, we are looking at it as a constant applied force is then turned into kinetic energy

5. First Part of the Model • Launch, and powered ascent • Launch occurs at time t=0 • End of poweredascent is at • T=0, K=0 • Work done byengine results inat

6. Need to Find • The engine burns for 1.8 seconds • Free body diagram: or With the mass of the rocket at ~80g But now we have a value for constant acceleration …… we want distance

7. The result of this exercise … • The distance an object travels is • The acceleration is related to the velocity, and we know the time (1.8 seconds) • From calculus and physics What does this mean for us?

8. We will do this graphically • At time zero, the rocket is standing still • At time the rocket has been accelerating for 0.1 sec and, in this case, . • Every 0.1second thespeed increasesby

9. So how far did we go? • Remember, this is only a model up to , or 1.8 seconds • For example (not the answer) the average velocity is for 1.8 seconds • The distance is • Why did wewant this?

10. The work done is converted to kinetic energy …. • Work done with: and: And Now you do it!!!