Of course, a vehicle is truly useful when it can move by itself on a level surface, or even up along a hill. This requires internal means of propulsion. In today's activity, groups will build and evaluate mouse trap racers using the engineering design process. The elastic potential energy in a set mouse trap is the means of propulsion. Show students Figure 1. A typical racer consists of a cart taped to a mouse trap.
A piece of string is attached to the swinging trap bracket. In operation, this string is wound around the driving axle in this case, the rear axle , which also sets the trap. The driving wheels are held tightly until the launch. Usually, it is best to remove the trigger pin and hold on to the driving wheels, since this makes for a well-controlled and repeatable launch. Let's see an example. Demonstrate using a racer built in advance. What performance criteria can we use to evaluate a racer design?
Let's first predict typical racer behavior. We can expect that during the launch, the racer will accelerate for as long as the string exerts a torque on the driving axle. The maximum velocity will be achieved just at the point when all of the string has unwound. This occurs when the mouse trap has shut closed. The racer will then gradually come to a stop as friction forces act to oppose its forward motion. Therefore, one way to quantify the racer performance is by means of a table of values for the following quantities:.
Ideally, we would like the largest possible values for all these quantities, except top deceleration, which we would like to be as close to zero as possible. In other words, we would like to minimize friction forces. Since we will have access only to acceleration measurements, we will need to compute velocity and distance traveled from the measured acceleration versus time graph.
Is it possible to design a racer with the best possible values for all four parameters? Are there any compromises your team has to make? Once in your teams, begin by diving into steps 1 and two of the engineering design process: ask to identify needs and constraints and researching the problem for this activity.
In this activity, "acceleration" will be used only for positive changes in velocity. Sharing Experiences: Lead a class discussion about student experiences with cars. Who likes sporty sedans? The Statistics Worksheet explains why several runs are conducted during the experiment instead of just one.
The Analysis Worksheet explains what is done to convert acceleration to velocity, and then to displacement, without calculus. It does not matter which is completed first, and alternatively, assign the worksheets as homework. Collaborative assessment of group results: Lead a collaborative effort to make sense of the activity.
Discuss what worked and what didn't. Each group built a unique racer, and should have obtained different insights into how physics laws applied to their designs. Discuss which racer scored better in each of the four metrics top acceleration, top deceleration, top velocity, total distance travelled , and why a tab on the Data Analysis Spreadsheet should help.
Ask students if any one design outperformed in all categories, or did students find different designs excelled in only one or two categories? Discuss how concepts of engineering design trade-offs apply. Ask students to suppose they were challenged to repeat the activity, but with actual application requirements. How would the insights they gained be used to craft a racer to satisfy the unique application requirements they were provided?
Try to include every student in this discussion to get as many possible ideas and insights as possible shared with the class. Collect the To Submit data from all teams, and make plots of performance metrics vs. Lead a collaborative class discussion. Ask the students:. Answer: In general, a racer with a smaller mass and larger diameter wheels has a larger top acceleration.
The wheel mass and particularly mass distribution is therefore another important factor to consider. Answer: Wheels with larger diameter travel a longer linear distance, and of course, the longer the wheels experience torque from the wound string, the further the racer travels. Answer: This question asks students to make the "data vs.
For example, the racer comes to a complete stop zero final velocity , and always travels forward no decrease in displacement , and any deviations from this in the data should be due to shortcomings in their data analysis techniques. Answer: The constant acceleration model is not accurate, since it does not account for Hooke's law, but it is much simpler than the linear model. Have students look at the linear model and see if the slopes of the segments are small enough to be approximated with constants.
What is meant by "small enough" is a great subject for a class discussion. Answer: Model 2 is more accurate, since it attempts to account for the fact that the torque exerted on the trap bracket is proportional to the bracket angle.
Curious students may wish to derive the exact behavior of the trap, which is beyond the scope of this activity. Warn students to exercise caution when setting the mouse trap. Keep fingers away from the bait area and sharp or rough edges. Inertia spinning button. How to Build a Mousetrap Car, Part 1 of 5.
However, these contents do not necessarily represent the policies of the NSF, and you should not assume endorsement by the federal government. Why Teach Engineering in K? Find more at TeachEngineering. Quick Look. Full design process. Print this activity.
Suggest an edit. Discuss this activity. TE Newsletter. Subscribe to TE Newsletter. Legacy Curriculum Hey there! This curriculum is no longer being curated or supported. It may contain materials that are no longer available or outdated information. Please use this document for reference. We're here to help: leave us a comment. Summary Students design, build and evaluate a spring-powered mouse trap racer using the engineering design process. They use acceleration data collected during the launch to compute velocity and displacement vs.
In the process, students learn about the importance of fitting mathematical models to measurements of physical quantities, reinforce their knowledge of Newtonian mechanics, deal with design compromises, learn about data acquisition and logging, and carry out collaborative assessment of results from all participating teams. Engineering Connection Automotive engineering is a branch of engineering concerned with all aspects of automobile development.
Grades 9 - 12 Do you agree with this alignment? If you can t move the Mouse the full amount shown on the Action card or can't move it at all because there aren't enough cards in the row or column, move it as far as you can and stop. Do not change the direction the Mouse is facing. Take all of the cheese pieces that are on the card the Mouse ends its move on leave the ones it passes over , and place them facedown in front of you.
This cheese is not safely out of the Maze yet, but if you finish your turn with- out getting ' trapped, it's ' all yours! If you get trapped, you lose the cheese.
Too' bad! Follow the instructions on the Maze card that the Mouse ends its move on. You may have to move again, place more cheese, or do some other wacky thing. Keep following the Maze cards' instructions until the Mouse can't move anymore.
Ignore all of the cards the Mouse passes over - just follow the instructions of the one it ends its move on! If you can't complete a Maze card's instruction because there aren't enough cards in the row or column go as far as you can and stop.
Once the Mouse has stopped moving and doing things to the Maze, if you are not trapped, you can either:. Repeat step 3: Try to get more cheese by continuing your turn. To continue, draw another Action card and do what it says - be careful, if you get trapped you lose your cheese! End your turn: Play it safe and end your turn now by saying that your turn is over.
You made it safely out of the Maze and you get to keep your cheese! Flip all of your facedown pieces of cheese faceup and wait for your next turn.
In either case, your turn is immediately over. You didn't make it safely out of the Maze, so you must give back all of the cheese you collected this turn these are the facedown ones. Take all of these cheese pieces and put them back into the cheese pile. Better luck next time. There are three cards that allow you to flip a Maze card.
To flip a card, turn it over so that its back is now faceup. Any cheese on a flipped card gets put back into the cheese pile. There are three cards that allow you to turn a Maze card. Important: Leave the Mouse on the card as you turn it This will make the Mouse face in a different direction as well.
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