Science 7–10 · Year 7
Ramps: force needed to pull a trolley up a slope at different angles
Physical sciences — Forces (NSW Stage 4 focus area)
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The idea
A ramp lets a smaller force move a load upward because only part of the load's weight acts along the slope, and the part grows as the slope steepens.
What you need
- wooden ramp board 1.0 m, 1
- dynamics trolley with 500 g total mass (trolley plus masses), 1
- 0 to 5 N newton meter, 1
- wooden supports or a lab jack to set the ramp height, 1
- metre rule, 1
- protractor to measure the ramp angle, 1
How to do it
- Weigh the trolley with its load; record the weight in newtons (mass x 9.8).
- Set the ramp's raised end 17 cm above the bench so the 1.0 m board makes about 10 degrees. Record the height and measure the angle with the protractor.
- Hook the meter to the trolley and pull it up the ramp at a slow, steady speed, keeping the meter parallel to the board. Record the reading; repeat three times.
- Raise the ramp to 34 cm (about 20 degrees), 50 cm (30 degrees) and 64 cm (about 40 degrees) and repeat the three pulls at each angle.
- Plot the pulling force against the angle and describe the pattern: does doubling the angle double the force?
- Compare the force at 30 degrees with half the trolley's weight.
What you should see
For a 0.500 kg trolley (weight 4.90 N) the steady pull rises as the ramp steepens but stays below the full weight: for a trolley with no friction it would be 0.85 N at 10 degrees, 1.68 N at 20 degrees, 2.45 N at 30 degrees and 3.15 N at 40 degrees, and the measured values are a little higher because of rolling friction. Doubling the angle from 20 to 40 degrees does not quite double the force, so the graph bends over slightly at the steeper angles. The learner knows it worked when the 30 degree pull is close to half the weight.
What changes
- What you change
- angle of the ramp (set by its height)
- What you measure
- force needed to pull the trolley up at steady speed (N)
- What you keep the same
- same trolley and load
- meter kept parallel to the ramp
- same slow steady speed
Common misconceptions
Each of these ideas is wrong, and the activity is a chance to test it.
- The force needed on a ramp equals the whole weight.
- Doubling the angle doubles the force.
- A ramp reduces the energy needed to lift a load.
Safety card
Hazards
- trolley rolling back down onto hands
- ramp slipping off its support
Controls
- a second learner catches the trolley
- secure the raised end with a clamp or non-slip mat
Note
No hazardous chemicals or naked flames are used. Complete the school's risk assessment for the activity before the lesson; the NSW Department of Education Science safety and compliance page points to CSIS 1.7 (Risk assessment – a pre-requisite for risk control) for how to carry it out.
Curriculum references
The NSW syllabus outcomes and Australian Curriculum v9 codes this activity supports. They are references, not a verified or complete curriculum alignment.
- Science 7–10 Syllabus (2023)SC4-FOR-01SC4-WS-04SC4-WS-05SC4-WS-06
- Australian Curriculum v9AC9S7U04AC9S7I02AC9S7I04AC9S7I05
Sources
The pages the author read to write this activity.