## Journey to the Earth’s Core

Name of Activity Journey to the Earth’s Core Kristen Burns and Sarah Halpert sturdy car, rock, travel, ramp, layers, earth, crust, mantle, core, axles, bushings, car, density, plate tectonics, mass, friction Simple Machines 4, 5, 6 1 Hour Total The kid’s needed to design a sturdy car that will hold a rock (small pebble). The car will then travel down a ramp that is labeled with the layers of the earth. The upper half of the ramp was the crust and the lower half of the ramp was the mantle. The floor directly after the ramp was labeled the outer core and following the outer core was the inner core section. The kids had to adjust the axles and bushings on the car to allow it to travel farther. Once the cars were finished we tested them on the ramp to see how far into the “earth” they went. Review density and how to measure the mass of an object Build a sturdy car and tweak it to allow it to travel the furthest down the ramp Learn the layers of the earth Simple Machine Kit Materials for a ramp Paper to cover the ramp that depicts the layers of the earth Small rocks Scales Get a large piece of paper and cut it down to fit the ramp while allowing some extra to account for the outer and inner core section. Design the paper with fun facts about each layer (temperature, thickness, etc.). Vocabulary: Density Plate Tectonics Mass Axle and Bushing Friction 1. Explain density and the theory of plate tectonics. Also, review how to measure the mass of an object. 2. Have them start building the cars. Make sure that the cars have a spot to hold the rock and that they are sturdy. Explain how to adjust the bushings to account for less friction. 3. Take the mass of the rock. 4. Test the cars on the ramp and see how far into the “earth” they were able to travel. 5. Fill out the worksheet. If a group finishes early ask them if they can make the car go further.

## Tow Truck

Name of Activity Tow Truck STOMP steep, ramp, tow, towing, weight, gears, gear up, gear down, building, design, friction, gravity, center of gravity NXTs 4, 5, 6, 7, 8, 9+ 1 Hour Total Build a car that can climb a steep ramp while towing a weight (10 batteries) behind it. Using gears to gear down is necessary for this challenge. This activity is more challenging than a regular ramp climb and may require some complex building and design. - To learn to build and use gears. - To learn about gravity, center of gravity, and friction. NXT kits ramp batteries for weight string computers running NXT Software Build a ramp. Set up computers running NXT software. Arrange student in groups of two. Distribute necessary materials. It is more difficult for cars to climb steep slopes for different reasons. In this lesson you can discuss with the class these different forces that affect the ability of the car to climb the slope: Friction – friction is the force acting between the surfaces of the car (tires) and the ramp surface. This is the force that keeps the car from slipping. Gravity – gravity pulls down directly towards the center of the earth. On a flat surface gravity does not pull a car in any direction, but just keeps it in place. On a slope, gravity pulls a car backwards towards the center of the earth down the ramp. Center of gravity – Center of gravity is the exact spot on an object where there is the same amount of weight on one side of the spot as there is on the opposite side. A high center of gravity means a car is more unstable on a steep slope. A low center of gravity close to a ramp will help the car stay on the ramp.To overcome these forces there are several things that you can do to your car: Low center of gravity – design the car to be low to the ground. Gear down the car – By adding gears to the motors and then gearing to the wheel you can increase the power of the motors, which will help the car climb the ramp. There is more information about gears and gear worksheets in the attached documents. Vocabulary: Gears Gear Ratios Gravity Center of Gravity Mass Friction Forces Have students design and build a car that will climb a ramp. Students will need to think about friction and center of gravity to build their car. If students are unfamiliar with these concepts, you should review the concepts with them. A car that is lower to the ground will be less likely to slip. Wheels that have more traction and greater surface area on the ramp will also be less likely to slip. Students will need to use gears to gain more power. If students are unfamiliar with using gears, you should review gears and gearing down with the students. Have students program their cars to move forward for 20 seconds. Allow students to test their cars on the ramp without anything in tow. Students should redesign the car if it does not climb the ramp. Students should then test their cars while towing the weight up the ramp and redesign until the car can tow the weight. If students have trouble tell them to try various gears, wheels and designs. What is the steepest ramp that the car can climb? What is the heaviest weight that the car can tow? Calculate the gear ratio. What is the quickest that the car can travel up the ramp? http://sites.tufts.edu/stompactivitydatabase/files/formidable/68_image_1.png http://sites.tufts.edu/stompactivitydatabase/files/formidable/68_image_2.png http://sites.tufts.edu/stompactivitydatabase/files/formidable/Engineering-and-Science-Skills1.doc http://sites.tufts.edu/stompactivitydatabase/files/formidable/Engineering_Design_Process3.doc http://sites.tufts.edu/stompactivitydatabase/files/formidable/Gear_Ratio_Worksheet1.pdf http://sites.tufts.edu/stompactivitydatabase/files/formidable/Gears_Worksheet1.pdf http://sites.tufts.edu/stompactivitydatabase/files/formidable/Tow_truck.doc