R11a – Using compound units: speed and density

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Prerequisites

A starting point: visually comparing speeds, distances, and times

Start with Alice and Bob, and click “Animate” to watch them go for a run. Then answer the three questions shown. After this, watch Clare and Dan go for a run, and answer the same three questions, before finally doing the same with Euan and Freya. You can check your answers below.

Answers to the above questions:

Alice and Bob

(a) Bob runs faster.

(b) Neither; they run the same distance.

(c) Alice spends more time running.

Clare and Dane

(a) Neither; they run at the same speed.

(b) Dan runs further.

(c) Dan spends more time running.

Euan and Freya

(a) Freya runs faster.

(b) Freya runs further.

(c) Neither; they run for the same time.

Part 1 – Speed, distance, and time

Teacher resources - Part 1 - Speed, distance, and time

  • Slides in PPTX (with click-to-reveal answers)
  • Slides in PDF (one slide per page, suitable for importing into IWB software)
Links to past exam and UKMT questions

Part 2 – Density, mass, and volume

Teacher resources - Part 2 - Density, mass, and volume

  • Slides in PPTX (with click-to-reveal answers)
  • Slides in PDF (one slide per page, suitable for importing into IWB software)
Links to past exam questions
In the real world

You can probably think of several real-world situations in which an understanding of speed, distance and time is helpful.

The concept of density is applicable to floating and buoyancy – which has many serious real-life applications. Can you think of some?

Objects less dense than water will float on water. But water is not the only medium things can float on. Here is a video of a cannonball floating in mercury, a metal which is liquid at room temperature:

Why do helium balloons float? Here is a video of an attempt to use helium balloons to lift a man off the ground:

What next?

An understanding of speed is needed before considering kinematic graphs: