Hand towing a car to promote critical thinking, Problem solving skills and Analysis.

Peter Groebner
Secondary Technical Education Program
1353 W. HWY 10
Anoka, MN 55303
Author Profile

Summary

In this active learning activity, students will find a technique to move a car with one hand. Students are given only a tow strap, so the students must apply angular force to successfully move the car with one hand.

Learning Goals

1) This activity is designed for students to use and enhance their critical thinking skills.
2) This activity requires students to utilize their problem solving skills.
Key concepts
1) Students will brainstorm solutions to the problem of moving the car with one hand.
2) After conducting the experiment students will be asked to answer questions located in the assessment section.

Key terms
-Scientific method
-Applied Force
-Net force
-Tension
-Vector diagram
-Inertia

Context for Use

This activity could be used in a Physics course or if the difficulty of the assessment is adjusted the experiment could be used in a general science course. The experiment can be conducted in a minimum of 45 minutes (depending on the input given by the teacher). The discussion should be based on applied force, force can be applied on a parked car if you push or pull on it with your hands. You can do the same with a tow strap, but with more possibilities. Even without using pulleys, you can multiply the forces you exert.

Subject: Physics
Resource type: Lab Activity
Grade level: High School (9-12)

Description and Teaching Materials

The experiment can be conducted in a minimum of 45 minutes (depending on the input given by the teacher). The discussion should be based on applied force, force can be applied on a parked car if you push or pull on it with your hands. You can do the same with a tow strap, but with more possibilities. Even without using pulleys, you can multiply the forces you exert. The students will be challenged to exert far greater force with brains than with muscle.

Materials:
-Tow strap rated for the minimum weight of the vehicle to be towed.
-Parking lot with access to a light median within 15 feet (this lab requires a level asphalt or concrete surface with access to a light pole to fix tow strap one end to the light pole one end to the car).

Description (Procedure)
1) Park the car on a level surface with the light median in front of the car, the car should be placed in park, fix the strap to the light median and the car, slowly roll the car away from the light median until the tow strap is taught.
2) The goal is to move the car closer to the light median. The students will do this by exerting force on the tow strap that is secured to the light median and the front end of the car. How and where the force is exerted is up to the students. The students' body is the only energy source that can be used. The students must make a sketch of the method and must show the applied force and resultant forces with vector diagram.

Teaching Notes and Tips

Safety guidelines;
*Select an area where the surface is free of loose rocks or gravel.
*The instructor should fix both ends of the tow strap and roll the car to apply tension to the strap.
*The students must not allow the car to roll free back into position the tow strap must be kept under constant tension.

Common Confusion: Often times when the students are given the problem they will naturally apply the force to the tow strap in parallel not at an angle. The instructor may need to lead the students to think about applying force at angle to the car and the light median.

The past the lab designed by Paul Hewitt calls for the car to be placed in park. The problem with the car being in park is the students must apply a larger amount of force to the tow strap which is in my opinion increases the students risk of slipping or the tow strap coming loose.

Assessment

I prefer the students work in randomly selected pairs.
1) A Vector diagram is required including a minimum of three forces interacting. Since the system is not accelerating, all forces must be in equilibrium. The students will use a vector diagram to explain how a small angular force can result in a large force to move the car.
2) List other situations that could use this technique for "force multiplication".
Answer: Bow and Arrow, Crane riggings etc.
3) This method for making a large force is used to fell trees, pull stumps, straighten dents in car fenders and tow heavy vehicles out of ditches. Explain how this is possible using your vector diagram as a guide.

Standards

1A Understanding major concepts.
1H Engage students in generating knowledge and testing hypothesis.
7B Plan instruction using contextual considerations that bridge cirriculum and student experiences.

References and Resources