Drag masses between the tray, the hanger and the trolley. Drag the light gates and the metre rule. Then press Release trolley.
Results
Shaded columns are calculated: F = hanging mass × 9.8 N/kg, a = (v − u) ÷ t, total mass = trolley + masses on trolley + hanging mass. Turn them off in the teacher options so students calculate them.
Graph
Method
- Measure the length of the interrupt card with the metre rule (use the magnifier) and type it into the data logger.
- Weigh the trolley on the balance with no masses on it and record its mass above the results table.
- Compensate for friction: unhook the string and use Push test. Raise the ramp until the logger shows the same velocity at both gates.
- Place the light gates so the card passes through both before the hanger reaches the cushion. Measure the distance between the gates with the metre rule.
- Investigating force: start with all the masses on the trolley and only the hanger on the string. Release the trolley and record the results. Move one mass from the trolley to the hanger and repeat. The total mass stays the same.
- Investigating mass: keep the hanging mass the same. Add masses from the tray to the trolley one at a time and repeat.
- Calculate a = (v − u) ÷ t, or use v² − u² = 2 × a × x with your measured distance between the gates. Repeat each reading and plot your graph.
Tips, safety and teacher options
- The data logger calculates velocity = card length ÷ time the beam is blocked, so the card length must be entered correctly.
- If the hanger lands on the cushion before the card reaches gate 2, the trolley is no longer accelerating and the result will be too low.
- The logger times t from when the card enters gate 1 to when it enters gate 2, so (v − u) ÷ t gives a slightly low acceleration. Using v² − u² = 2 × a × x with the measured gate separation avoids this – a good discussion point about systematic error.
- Safety: a cushion catches the falling mass, the trolley is stopped by an end stop, and the masses are taped to the trolley.