Inclined Plane Spring Scale

Use a spring scale to compare the effort required to lift a 1000g mass straight up versus pulling it along an inclined plane at different angles. Students observe that a gentler slope reduces the required force, illustrating mechanical advantage and the tradeoff between force and distance.

1. Gather a spring scale, a 1000 g mass (or similar), a sturdy board to use as a ramp, blocks/books to change the ramp angle, and a model “truck bed” or raised platform.
2. Measure the force to lift the mass straight up: attach the spring scale to the mass, lift just off the table, and note the reading (about 1000 g-force for a 1000 g mass).
3. Set a moderate ramp angle by propping up one end of the board. Place the mass at the bottom, attach the spring scale, and pull the mass smoothly up the ramp while keeping the scale parallel to the ramp. Record the force (expect less than lifting straight up, e.g., ~500–700 g-force).
4. Lower the ramp to a gentler angle and repeat the pull, recording the new (smaller) force reading (e.g., ~250–500 g-force).
5. Raise the ramp to a steeper angle and repeat once more, noting that the required force increases toward the direct-lift value as the ramp approaches vertical.
6. Discuss the tradeoff: on shallower ramps you apply a smaller force over a longer distance to reach the same height.
7. Extension: show that a screw can be modeled as an inclined plane wrapped around a cylinder (use a strip of paper with a drawn diagonal line and wrap it around a dowel).

Simple Machines: The Inclined Plane - funsciencedemos:

📄 SIMPLE MACHINES INCLINED PLANE - eisco: https://d4iqe7beda780.cloudfront.net/resources/static/main/pdf/eis0010sm.pdf

• Use a protractor to measure ramp angle and plot required force versus angle.
• Keep the vertical rise fixed; vary ramp length and compare effort to the length traveled to estimate ideal mechanical advantage (IMA ≈ ramp length ÷ vertical rise).
• Test different surface coverings on the ramp (plastic sheet, felt, sandpaper) to explore friction’s effect on the required force.
• Compare sliding versus rolling by repeating the test with a small cart or dolly and noting the much lower force.
• Try different masses and see whether the ratio of effort (on the ramp) to weight (direct lift) stays roughly consistent at a given angle.

• Stabilize the ramp and supports so they cannot slip or tip.
• Keep fingers clear of pinch points under the ramp and near the supports.
• Pull steadily—do not jerk the spring scale or overload it beyond its rated capacity.
• Secure the mass so it cannot roll or slide uncontrollably; catch from the side, not in front of the moving object.
• Use proper lifting posture if handling heavier objects.

• Why does a shallower ramp require less force for the same height gain? (Because the same work is spread over a longer distance, reducing the force needed.)
• If the ramp were vertical, what would the scale read? (About the full weight—no mechanical advantage.)
• How does increasing ramp length for the same vertical rise affect mechanical advantage? (It increases IMA, so less effort is needed.)
• What role does friction play in your measurements? (Friction adds extra opposing force, so the measured effort is higher than the ideal prediction.)
• How is a screw related to an inclined plane? (A screw is an inclined plane wrapped around a cylinder, trading distance turned for reduced input force.)