Ramps: lifting a load the easy way
Load a sack of rice onto a truck. Lift it straight up, then push it up ramps of different lengths, on a trolley or dragged, and see how much push each one needs.
Core concept
In short: Push a load up ramps of different lengths: a longer ramp needs less push.
A ramp is a simple machine: a longer ramp needs a smaller push, but you push the load a longer way
Topic: Simple machines
Lifting a heavy sack of rice straight up onto a truck is hard: you have to push up with a force: A push or a pull. Forces can start, stop or turn things. All key words as big as its whole weight: The pull of gravity on something, measured in newtons. It is less on the Moon. All key words. Loaders lean a long plank against the truck instead and push the sack up the plank. A sloping surface like this is a ramp, or inclined plane, and it is one of the simple machines. The ramp holds up part of the load for you, so you need a smaller push (the effort). But nothing comes for free: on a longer, gentler ramp you push for a longer distance. Wheels help too, because a sack dragged up the ramp rubs against it.
What you will learn
- Measure the push needed to move a load up ramps of different lengths.
- Explain why a longer ramp needs less effort but a longer push.
- Say how many times easier a ramp makes a job.
- Explain why wheels make pushing a load up a ramp easier.
Before you start
- Know that weight is a force measured in newtons (N).
Materials
- A sack of rice (or a box of books)
Equipment
- A strong plank, a trolley, a spring balance that reads in newtons
Procedure
- Lift the 200 N load straight up onto the truck and record the push.
- Push the load up a 2 m ramp and record.
- Try every ramp length and record each one.
- Drag the load up as a sack instead of on a trolley and record.
- Push a heavier load up the 4 m ramp and record.
How this simulation is simplified
- The truck's floor is 1 m above the road.
- The trolley's wheels roll without rubbing; a dragged sack rubs with a friction of 0.2 of the part of its weight that presses on the ramp.
- The load is pushed up slowly and steadily, along the ramp.