Analysis of Rocket
Height and Data
Purpose: To predict the height of a rocket from a taking
measurements of thrust and total time of thrust. Launch Rocket and verify
predictions.
Equipment: Model Rocket, thrust engine, computer with data
logger and excel software, rocket stand
1. Draw a system
schema and force diagram and apply Newton's Second Law to a rocket on the
launch pad.
2. Redraw the
system schema and force diagram and a statement of Newton's Second Law right based
on this force diagram for the moment the rocket leaves the ground.
a. What agent is causing the upward force?
The only upward
force on the rocket as it accelerates upward is the thrust force pushing on the
air
b. Do you think the thrust force is constant? Explain
The force is not
constant because the fuel is changing, with time. The same amount of fuel isn’t being used
constantly
3. As the fuel
burns, is your rocket speeding up or slowing down? Which force has to be bigger
for this to occur? Do you need to modify your force diagram?
Since the net
force acting on the rocket is F thrust – Fg, where Fg = mg. The net force upward is increasing because mg
is decreasing due to the loss of fuel.
4. Your rocket is
not a particle. Do you think you have to deal with air resistance?
Redo your system
schema, force diagram and statement of Newton's Second Law to include it.
Air resistance is
dependent on the velocity and the surface area.
Therefore as the rocket is speeding upwards the air resistance is
increasing. The formula to calculate the
drag force on the rocket is kv^2.
5. Do you think F
air is constant? If not, what does it depend on?
F air is not
constant and depends on velocity.
6. When the
rocket has run out of fuel, what does direction is it still going? Is it
speeding up or slowing down? Based on this what does your force diagram look
like now. What is your new statement of Newton's Second Law?
The rocket is
moving with an upward velocity after the rocket has fun out of fuel. The rocket will continue upward until
velocity equals zero, the rocket slows down because the net force is pointing
downward. Fnet = -mg - Fair
7. How will you
know when the rocket reaches its highest point?
The highest point
is when the rocket seizes to move upward, this occurs when velocity is zero.
10. What specific
information and measurements do we need?
Specific info:
Mass of rocket, cross-sectional area of rocket, air density, force of gravity
Measured info: thrust
force of rocket, time, velocity, acceleration, drag force, position
Procedure: The rocket engine was placed securely on a
stand with a force sensor attached. The
engine was then ignited and allowed to run out of fuel. While the engine was running we used the data
logger software along with the force sensor to take a measurement of the thrust
force. The data file gave us a
measurement of the thrust over time.
We
then measured the mass of the rocket, which was found to be 63.2 grams. Also the diameter of the rocket was measured
in order to calculate the cross sectional-area.
We calculated the acceleration by using Newton’s second law Fnet = ma or
a=Fnet/m. In our case the calculation
was
Fnet = (Fthrust – Fdrag – Fg)/m
Putting the data
for thrust versus time along with the calculation for acceleration and the kinematic
equations we found all the data needed to predict the height.
It was important
to find the data in a specific order to get accurate results the order was
time, thrust, acceleration, drag, delta r, and r. The height found was 147 meters.
The rocket was then launched, after the rocket landed the altimeter was checked and out predictions were verified, the max height was 147meters