Lab 6 Practice

Buoyant Force, from the OnRamps Lab 6 worksheet. Float a wooden block, use Archimedes' principle to work out its mass, then check it against the scale. Every run gives new, realistic data.

Goal: use density, Archimedes' principle and the buoyant force to find the mass of a floating rectangular block experimentally, then compare it to the block's mass measured on a scale. You also have to measure the density of your liquid.

Key formulas

F_b = W_fluid = ρ_liquid V_sub gArchimedes: buoyant force equals the weight of liquid displaced.

Floating: F_b = mgNet force is zero, so buoyant force balances the block's weight.

m_exp = ρ_liquid V_subg cancels. In g and cm³ this gives grams directly.

ρ = m / VLiquid density from a graduated cylinder on the scale. 1 mL = 1 cm³.

V_sub = L × W × dRectangular block: d is how deep the bottom sits below the waterline.

Δx = s / √N, 95% CI = mean ± 2Δxs is the sample standard deviation (divide by N − 1).

Part 1Design your experiment

Pick a liquid and a way to find the submerged volume. On the real worksheet you write the materials, the set-up, the data to collect, sources of uncertainty and how you'll analyze it, plus an annotated sketch and numbered steps. Try writing yours before opening the sample.

Rubric check (Part 1 is worth 40 points)

My design gives data that find the liquid's density and the block's experimental mass, plus a scale mass to compare. My sketch shows every piece of equipment, labels for every measurement, and arrows for the buoyant force and the weight. My steps for the liquid density are clear enough for another student to copy. My steps for the block's mass are clear enough for another student to copy.

Show a sample design for this set-up

Part 2aMeasure the liquid's density

Each trial: weigh the empty graduated cylinder, pour in some liquid, read the volume at the bottom of the meniscus, weigh again. Fill in the liquid's mass and its density. A box turns green when you're within 2%.

Part 2bFloat the block and find its mass

Scale reading of the dry block

Q195% confidence interval of the experimental mass

mean = Σxᵢ / Ns = √[Σ(xᵢ − mean)² / (N − 1)]Δx = s / √N95% CI = mean ± 2Δx

Quantity	Liquid density ρ (g/cm³)	Experimental mass (g)

The worksheet only asks for the mass CI; the density column is extra practice. Statistics checks allow 3%, since rounding adds up.

Q2Interpretation of findings

Does your measured (scale) mass fall within the 95% confidence interval from Q1? Explain what that means.

1. Is the scale mass inside the 95% CI of the experimental mass?

2. So what can you conclude?

3. Is your experimental average higher or lower than the scale mass, and what's a likely cause?

Show the worked solution for this data

Show a sample answer for Question 2