Physics IA · A · Space, time and motion · topic 4 of 30

Trolley on a ramp: how much energy does friction take? · IB Physics IA idea: guide, sample graph and step-by-step plan

a classic energy test: simple, but it can go deep

Textbooks say a trolley at the bottom of a ramp has the speed of a free fall from the same height. Your job is to show how far from ideal your ramp really is.

Difficulty●●○ Medium
KitStandard: trolley, ramp, light gate or phone video
TimeAbout 10 hours
FitsSL and HL
  • ✓ you like clean energy ideas
  • ✓ you can use a light gate or slow-mo video
  • ✓ you want a result you can check against theory

The big idea

← the GAP is your RQ hook!

If no energy were lost, mgh would turn entirely into ½mv², so v² = 2gh and a graph of v² against h is a straight line through the origin with gradient 2g. Real trolleys fall short: friction and the wheels' own motion take a share. The gap between your line and the ideal one is the story. Predict its size, measure it, then ask whether it stays a fixed fraction of the energy as h changes. A graph of v² against h turns an energy loss into a gradient you can compare.

Make it yours: pick one twist

Copying a classic won't show your choices. Pick one of these (or invent your own) and your IA becomes yours.

Swipe for more twists →

Change the ramp angle

Repeat the height series at two or three angles.

→ Friction on a gentle slope takes a larger share of the energy; your analysis can test whether the lost fraction depends on angle.
Change the surface

Cover the ramp with paper, felt or sandpaper while keeping the trolley the same.

→ A new variable that changes the gradient directly; the lost fraction becomes a measure of the surface.
Separate friction from rolling

Compare a trolley with a block sliding on a low-friction film.

→ Splits the two loss mechanisms; needs extra theory for the wheels, so best for HL-style depth.
Track speed along the ramp

Use video or two light gates to find speed at several distances for one release.

→ Graph becomes v² against distance; tests whether acceleration is constant along the slope.
Add a launch step

Let the trolley leave the ramp and land, then use projectile motion to find its speed.

→ A second, independent route to v that you can compare with the gate; the evaluation compares methods.
Change the context

Frame it as a roller-coaster drop, a skate ramp or a rolling-resistance test.

→ Gives your introduction a purpose; the method and the graph stay the same.

Your Physics IA research question: run the check

Write your own question first. Then make sure it ticks every box:

  • Names one independent variable and its range (which heights, how many, how you set them).
  • Names one dependent variable and how it is measured (speed at which point, by what method?).
  • Says what stays fixed (angle, trolley mass, surface, start from rest).
  • Says what you compare with (the frictionless prediction, and what you will conclude about the loss).
  • Is narrow enough for about 10 hours, with at least 6 heights and repeats at each.

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The set-up

One way to arrange it. Sketch your own with real measurements: ramp length, angle, gate position and flag width.

hθtrolley + flag: same mass every runlight gate: times the flagsame angle every runh: upright, not along the slope

How your Physics IA could be laid out

The usual order for a topic like this, what each part needs to show, and roughly how much of your 3,000 words it takes. The words are all yours.

Research question and context~250
Your question; where energy losses matter (vehicle ramps, rides); what you expect and why.
Background physics~450
Gravitational potential energy to kinetic energy; why v² = 2gh if nothing is lost; how friction and rolling change it; how a flag and gate give speed.
Variablestable
Independent, dependent and controlled variables, each with how you set, measure or hold it, and why it matters.
Method~400
Apparatus with resolutions; how h is measured (vertical!); how the trolley is released from rest; where the gate sits and why; repeats.
Safety, ethics, environment~50
Short and specific: falling trolley, tidy floor.
Raw datatable
One table: height, each timed reading, flag width, units and uncertainties in the headers.
Processing~250
Flag width and time to speed, speed squared, and the uncertainty on each; one worked example per calculation type.
Graphs and analysis~400
v² against h with error bars and best-fit and worst-fit lines; what the gradient means; the ideal line drawn for comparison.
Conclusion~400
Answer with numbers: how far below the ideal gradient you are, and whether the lost fraction depends on h.
Evaluation~650, the biggest part!
Weaknesses ranked by their effect on your result, each linked to a specific improvement.
Referencesnot counted
Every source for theory and method.

What your Physics IA graph could look like

draw the ideal line too ✓

Made-up data, to show you the form of a strong graph, not the answer. Yours will look different. example only

0.000.050.100.150.200.250.300123456Release height h / m (± 0.002 m)Speed squared v² / m² s⁻² (± 0.15)model with frictionno losses: v² = 2ghyour data, with error barsthe gap between the lines isthe energy lost: how big, and doesit stay a fixed fraction?ILLUSTRATIVE · MADE-UP DATA
  • The axes are chosen so the ideal theory is a straight line through the origin: easy to test.
  • Error bars on every point. Speed squared roughly doubles the fractional uncertainty in speed, so say how you propagated it.
  • The ideal line is drawn too, so the reader sees the gap, not just your points.
  • The best-fit line should be allowed an intercept. Does yours pass through the origin, and what would a non-zero intercept mean (for example gate position)?
  • Another graph to consider: energy lost, (mgh − ½mv²), against h, which should be a straight line if friction does constant work per metre.

Which uncertainty matters most?

Rank by the effect on your result, here the small fraction of energy lost, not on the raw readings. A loss of about a tenth magnifies every small error in v and h.

Gate time (± 0.5 ms)30%Flag width (± 0.5 mm)16%Release height (± 2 mm)8%biggest effect: discuss this first!% uncertainty in the fraction of energy lost, release from h = 0.20 mILLUSTRATIVE · MADE-UP NUMBERS

Your game plan

do a trial run first!

Tick steps off as you go. We'll remember on this device.

0 of 11 done

  1. Read and predictFind the energy argument for v² = 2gh and how friction and wheel rotation change it. Write down your prediction for the gradient of v² against h, and why it should differ from 2g.
  2. Trial run (1 lesson)Roll the trolley from a few heights. Does the flag cut the beam cleanly? Is the release really from rest? Does the time repeat to the millisecond?
  3. Decide range, repeats and timingChoose at least 6 heights spread across the ramp, how many repeats, and where the gate goes. Write down why: it becomes method justification.
  4. Measure the fixed thingsRecord ramp angle, trolley mass, flag width and their uncertainties before the main run, so you can state what stayed fixed.
  5. Collect the dataRecord raw readings straight into the table with units and resolution. Note anything odd as it happens.
  6. ProcessConvert flag width and time into speed, square it, and carry the uncertainty through. Decide how you treat the average speed over the flag.
  7. Graph and fitPlot v² against h with error bars, fit the best and worst lines, and read off the gradient. What should it be if friction were zero?
  8. Compare with theoryExpress the energy lost as a fraction. Is it the same at every height, within your uncertainties? Does that fit friction doing constant work per metre?
  9. EvaluateRank the weaknesses by effect on the lost fraction, not on raw readings. Make each improvement answer one weakness.
  10. Write, then cutWrite in the order of the layout above and stay within 3,000 words. Tables, graphs and references do not count, so let them carry detail.
  11. Check before your teacher's draftRun through the checklist below, then get your RQ or draft checked. Your teacher reads one draft only.

Physics you'll need

Traps to avoid in this Physics IA

  • Assuming the ramp is frictionless and then blaming the gap on "human error".
  • Measuring h along the slope instead of vertically.
  • Too few heights, or a narrow range, so the gradient is poorly defined.
  • A flag so wide that its average speed differs noticeably from the speed at the gate.
  • Releasing with a push, so the trolley does not start from rest.
  • Changing the angle as you change the height (stacking books under the ramp without re-measuring).
  • An evaluation that never says how large the lost fraction is, or how sure you are of it.

More Physics IA ideas like this

Make sure it's yours

This guide shows how a topic like this is usually approached. It is not an IA. Your question, choices, data, analysis and words must be your own: change something, tell your teacher where the idea came from, and follow your school's rules on outside help.

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