Truck Pull

Materials:

• An 8,000 pound SUV (Mr. Peake's Ford Excursion)
• A 25-meter 4-line heavy duty pulley system
• A 3-meter length of nylon rope with wooden handle
• An anchor point capable of withstanding several hundred pounds of force (a basketball goal post works well)
• Sidewalk Chalk
• Measuring Wheel

Preparation:

1. Find a level surface at least 20 meters in length with a solid anchor point (an outdoor basketball court works well)
2. Park the SUV so that the front tow hook rings are facing the solid anchor point, and at least 5 meters away (make sure the SUV is as closely in line with the anchor point as possible so you don't end up trying to pull the truck sideways)
3. Attach the 3-meter nylon rope to the tow hook ring farthest from the solid anchor point
4. Attach one end of the pulley system to the tow hook ring closest to the solid anchor point
5. Attach the other end of the pulley system to the solid anchor point (goal post)
6. Mark the pavement in 1-meter increments in front of the SUV from the point where each handle rests on the ground

Reflection:

• Why do you think you were able to move the truck farther with the pulley system than with the rope alone?
• Why did you have to go farther with the pulley system than the truck actually moved?
• How would you compare the amount of effort (force) needed for the rope alone vs. the pulley system?

Why it Works:

The scientific formula for calculating work is: force times distance, or w = f x d. We measure effort or force in Newtons, the distance in meters, and the work in Newton-meters (Nm), which is an expression of the force required times the distance traveled. The reason simple machines, like the pulley system in this experiment, make the work easier is that they allow us to spread out the work over a longer distance, which means we can use less force (effort). Can you apply that logic to this experiment and figure out why the truck didn't move as far as you had to pull the handle?