Choosing the appropriate sensor and equipment

One of the most important experimental skills students can develop is choosing the right equipment for the job.

When I design practical work, I deliberately provide students with a range of apparatus. Some items are clearly appropriate, some are workable but imperfect, and others are included specifically to make students think. The aim is not simply to collect data, but to justify decisions and evaluate outcomes.

A classic example of this approach is comparing two excellent motion-measuring tools from PASCO Scientific:

• the ultrasonic motion sensor

• the Smart Cart with built-in motion sensing

Both can measure motion accurately—but they are designed for different experimental questions.

---

Ultrasonic Motion Sensor

Best for: simple, linear motion

The ultrasonic sensor measures distance by emitting sound pulses and timing their return. It is ideal for:

• Distance–time and velocity–time graphs

• Trolleys moving in straight lines

• Introducing motion concepts at GCSE and early A-level

Why students choose it

• Quick to set up

• Very clear graphical output

• Excellent for conceptual understanding

Key limitation

• Not reliable for collisions, angled motion, or cluttered environments

---

Smart Cart Motion Sensor

Best for: dynamics, forces, and real-world motion

The Smart Cart measures motion internally, using encoders and sensors built into the cart itself. This makes it far more robust in complex situations.

Why students choose it

• Reliable during collisions

• Ideal for Newton’s laws, momentum, and impulse

• Works well with force sensors and varying motion

Key limitation

• More complex than necessary for simple motion studies

---

The Teaching Strategy

Rather than telling students which sensor to use, I might ask:

“You want to investigate acceleration during a collision. Which equipment would you choose, and why?”

Students must then:

• Select appropriate equipment

• Justify their choice

• Reflect on the quality of their data

This turns a practical from method-following into experimental design.

---

The Real Lesson

Good experimental results don’t come from expensive equipment alone.
They come from matching the tool to the task.

Learning to make that judgement is one of the most valuable outcomes of practical science—and motion sensors are a perfect way to teach it.