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Title: Using Balloon Rockets to estimate the effect of mass on acceleration.
Principle(s) Investigated:
Newton's Third Law of Motion states that, For every action there is an equal and opposite reaction.
Standards : Grade Eight California Science Content Standards
Forces
- Unbalanced forces cause changes in velocity. As a basis for understanding this concept:
- Students know a force has both direction and magnitude.
- Students know when an object is subject to two or more forces at once, the result is the cumulative effect of all the forces.
- Students know when the forces on an object are balanced, the motion of the object does not change.
- Students know how to identify separately the two or more forces that are acting on a single static object, including gravity, elastic forces due to tension or compression in matter, and friction.
- Students know that when the forces on an object are unbalanced, the object will change its velocity (that is, it will speed up, slow down, or change direction).
- Students know the greater the mass of an object, the more force is needed to achieve the same rate of change in motion.
Investigation and Experimentation
Investigation and Experimentation
- Scientific progress is made by asking meaningful questions and conducting careful investigations. As a basis for understanding this concept and addressing the content in the other three strands, students should develop their own questions and perform investigations. Students will:
- Plan and conduct a scientific investigation to test a hypothesis.
- Evaluate the accuracy and reproducibility of data.
- Distinguish between variable and controlled parameters in a test.
- Recognize the slope of the linear graph as the constant in the relationship y=kx and apply this principle in interpreting graphs constructed from data.
- Construct appropriate graphs from data and develop quantitative statements about the relationships between variables.
- Apply simple mathematic relationships to determine a missing quantity in a mathematic expression, given the two remaining terms (including speed = distance/time, density = mass/volume, force = pressure × area, volume = area × height).
- Distinguish between linear and nonlinear relationships on a graph of data.
Materials:
- Balloons. Oblong work best but regular balloons will work.
- String. Kite string or fishing line
- Tape
- Pennies or other form of mass.
- Fold style sandwich bags
- Meter sticks
- Ring stands or ? to tie string to
Procedure:
Form groups of 4 or 5 members.
- Tie one end of the string to a stationary object. A ring stand or chair will work, or you can tape one end of the string to a desk.
- Thread the string trough the straw.
- Tape the sandwich bag to the center of the straw to form a pouch to carry penny passengers.
- Using the balloon pump. Use fifteen full pumps to blow up the balloon. Manually hold the open end of the balloon closed.
- Using two pieces of tape. Tape the balloon to the straw.
- Pull and hold the string tight, horizontal to the ground.
- Beginning at the zero meter mark, release the balloon.
- Measure the distance traveled along the string.
- Repeat, adding mass (passengers) to the straw.
- Insert data into MY DATA
SEE (VIDEO 1) BELOW FOR PROCEDURE
Student prior knowledge:
- Mass: mass and weight are different. Mass is independent of force.
- Velocity: if an object's speed and direction are constant, the object's velocity is constant.
- Acceleration: is the difference in velocity over time for a given distance.
- Unbalanced Force: the change in velocity of a stationary object is caused by an unbalanced force acting on the object.
- Friction: friction is a force, that when unbalanced, can change the velocity of an object.
Explanation:
A rocket, in its simplest form, is a chamber enclosing a gas under pressure.A small opening at one end of the chamber allows the gas to escape, and, in so doing, provides a thrust that propels the rocket in the opposite direction. A good example of this is a balloon. Air inside a balloon is compressed by the balloon's rubber walls. The air pushes back so that the inward and outward forces are balanced. When the nozzle is released, air escapes and the forces become unbalanced. The action of the escaping gas propels the balloon in a rocket flight. (NASA)We will be using Balloon Rockets to investigate Newton's Third Law of Motion. We will attempt to examine the forces that act on our balloon rockets by varying mass and resistance to the action of our rockets. In our experiment we will measure the distance the balloon travels as a relative measurement of the net forces acting on the balloon Newton's Second Law of motion is a mathematical equation that helps to explain the Third Law. The three parts of the equation are mass (m), acceleration (a), and force (F). Using letters to symbolize each part, the equation can be written as follows:
F = ma
The equation reads: force equals mass times acceleration. Force is the "action and reaction" in Newton's Third Law of Motion. If all other factors affecting Force (power source, friction, etc.) are equal, mass will only affect acceleration. Since mass is the independent variable, acceleration is the factor we are indirectly measuring when we measure the distance traveled. Mass is inversely proportional to acceleration.
F/m = a m^ = av
Therefore, we would expect to see a decrease in distance traveled as mass increases.
Questions & Answers:
1.Did mass alone change your results? Explain why.
Yes. The increase in mass caused the rocket to travel at a slower rate and not go as far. The mass increase caused the force to be greater opposite the action, lessening the effect of the action force. The net force of the balloon rocket would be less.
2. What were the combined forces acting on your rockets that caused them to respond to Newton's Second Law in the way that they did?
The action force was air pressure pushing against the increased pressure inside the inflated balloon, causing air to be expelled, propelling the balloon. The opposite (reaction) forces were air resistance, friction between the string and the straw, and the weight (mass x gravity) of the balloon complex.
3. Would you expect the same results using fishing line? Why or why not?
No. Fishing line has a smoother surface than string, so friction would be less. The opposite force would be less.
Applications to Everyday Life:
Skateboarding: A skateboarder is standing on a skate board and both are not moving. The skateboarder pushes off of the skateboard. The act of the skateboarder stepping off is the action. The skateboard moving off in the opposite direction is the reaction. The skateboarder moves forward a slight distance, say half a meter. With it's lighter mass, the skateboard moves in the opposite direction a great distance, say ten meters.
Cannons: A cannon fires a cannon ball with considerable speed and force. As the cannon ball is expelled from the cannon, the cannon recoils, The cannon ball moves a great distance but, the cannon does not. The greater mass of the cannon and the shorter distance moved is equal to the lesser mass of the cannon ball and the greater distance .
SEE (VIDEO 2) BELOW
Automobile Crashes: When an automobile in motion collides with a stationary object, the stationary object "pushes back" with a force that is equal and opposite to that of the the moving auto.
VIDEO 1: Balloon Rockets: a fun, at-home science experiment.
VIDEO 2:The Science of Firing a Cannon : action and reaction force
References:
Baker, G. (n.d.). Balloon Lab. Retrieved November 2011, from The Science Queen: www.thesciencequeen.net/balloon%20lab.doc
dizzo95. (2007, July 29). The Science of Firing a Cannon : action and reaction force. Retrieved November 19, 2011, from You Tube: http://www.youtube.com/watch?v=8deNwoczCPc&feature=player_embedded
Freedman, S. (2009, December 19). Balloon Rocket Lab. Retrieved November 17, 2011, from Physics & Physical Science Demos, Labs, & Projects for High School Teachers: http://teachingphysics.wordpress.com/2009/12/19/balloon-rocket-lab/
NASA. (n.d.). Liftoff to Learning: Newton in Space. Retrieved November 2011, from NASA Quest: http://quest.nasa.gov/space/teachers/liftoff/newton.html
scienceoffcenter. (2010, August 27). Balloon Rockets: a fun, at-home science experiment. Retrieved November 01, 2011, from You Tube: http://www.youtube.com/watch?v=A7wrEWfV6TY&feature=related
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