What it shows
An inclined plane lets you move a load up with less force than lifting it straight, but over a longer distance. The gentler the slope, the smaller the pull needed and the longer the path.
The science
Lifting a load straight up means working against its whole weight at once. A ramp spreads the same work over a longer distance, so the force needed at any moment is smaller. The steeper the ramp, the closer it gets to straight lifting and the more force it takes. Friction on the ramp adds a little force, which is why smooth ramps work best. Roads winding up hills and wheelchair ramps use this idea.
Materials
Cost: free. Many items come from home or from waste; spare parts such as LEDs, motors and wire are in the store.
- A stiff cardboard sheet or a wooden plank about 60 cm long
- A pile of books to raise one end
- A small toy car or a matchbox with a pebble in it
- A rubber band and a paper clip as the force meter
- A ruler and a strip of paper to record the stretch
Safety
This project uses safe, everyday materials. Still, read the rules below with a parent before you start.
Never use mains electricity: power models with cells, batteries or a low-voltage adapter. Sharp and hot tools, flames and lab chemicals need an adult or your teacher beside you. Keep magnets, button cells and small parts away from young children, and wash your hands after making.
All the safety rulesStep by step
8 steps. Do them in order, and test each part before you go on to the next. Write what you notice in a notebook as you go.
Hook the paper clip to the front of the toy car and loop the rubber band through it so you can pull the car with the band.
Lift the car straight up by the band and mark how far the band stretches on the paper strip; label it "straight lift".
Rest one end of the cardboard on two books to make a gentle ramp and pull the car slowly up it with the band.
Mark the stretch for this gentle ramp, pulling steadily, not in jerks, and measure the length of the ramp with the ruler.
Add two more books so the ramp is steeper and repeat the pull and the mark.
Add books a third time for the steepest ramp you can manage and mark again.
Arrange the marks in a table from gentlest to steepest and note that the stretch grows as the ramp gets steeper but stays less than the straight lift.
Draw a bar chart of the stretch for each height of books and write what it shows.
What you should see
The rubber band stretches least on the gentle ramp, more on the steep ramp and most of all for the straight lift. The gentle ramp needs the longest pull.
Viva questions
A teacher or a judge will ask how it works. Try to answer each question before you open it, then compare.
1What simple machine is a ramp?
An inclined plane.
2Why does a ramp make lifting easier?
It spreads the work over a longer distance, so the force at each moment is smaller.
3Is anything lost by using a ramp?
Yes, you have to pull over a longer distance, and some effort is wasted on friction.
4Give a real example of an inclined plane.
A road zig-zagging up a hill, or the ramp used to load a truck.
Take it further
Cover the ramp with a cloth and then with a smooth plastic sheet and see how friction changes the force needed.
Change one thing, measure what happens, and add a table or chart of your readings: that is what turns a model into your own investigation.
Free ebooks for this project
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