Grade 8 - Session 1: Speed & Acceleration with Ramps
Session Architect: Aleeza Ayaz - Markhor3D
Session Length: 50-60 minutes
Learning Objectives:
In this session, students will:
- Build custom ramps and explore how surface type affects speed and acceleration while keeping the ramp angle constant.
- Use photogate sensors connected to MeasureLab to measure the speed and acceleration of a cart on different surfaces.
- Understand how friction impacts the motion of an object on an inclined plane.
- Apply Newton’s Laws of Motion to understand the relationship between force, friction, and acceleration.
- Analyze data to investigate the relationship between surface material, speed, and acceleration.
- Identify independent, dependent, and controlled variables in an experiment.
- Graph the relationship between surface material and speed, and explore how friction and Newton’s Laws affect motion.
Teacher Resource:
Session File: ML81.plf (61.9 KB)
Equipment Required:
- PC/Laptop to display measurement and live plot
- Photogate sensors connected to MeasureLab for precise timing.
- Ramps set at a fixed angle.
- Carts or small rolling objects.
- Various surface materials (e.g., sandpaper, carpet, smooth plastic, rubber) to place on the ramps for friction tests.
- Measuring tape to measure the distance the cart travels.
- Worksheet for recording data and making observations.
- Pens, pencils, markers, etc.
Teaching Aids:
- Projector to display live data from MeasureLab’s photogate sensors (optional).
- Visual aids showing how friction and slope affect motion.
- Diagrams or visual aids for introducing speed, acceleration, friction, and Newton’s Laws.
Preparation:
This step has to be done before the session on each workstation/apparatus by the teacher/session instructor:
- Make sure that each computer has Physlogger installed and can detect the Measrelab when connected to it using the provided cable.
- Each Measurelab should have access to a power outlet for sensors that require external power. For this session, Photogate will be used which requires an external power source. The load cell is built-in and the photogates will be connected in the following ports:
Your setup will look something like this:
Introduction and Hands-On Exploration: (30-35 minutes)
Engaging Students with Everyday Examples of Motion:
- You may start by asking:
“Have you ever watched a car go down a hill or played with a toy car on a ramp? What do you think happens to the speed of the car as it moves down?”
-
Let students share their experiences, encouraging them to discuss how speed changes as the car moves down the hill or ramp.
-
You may build on their responses by saying:
“That’s because the car is accelerating! Today, we’ll build our own ramps and use sensors to measure how fast a cart moves and how quickly it speeds up, depending on the surface it moves on. We’ll also learn why friction affects how fast the cart moves.”
What is Friction and How Does it Relate to Newton’s Laws?
- You may continue by asking:
“Can anyone tell me what friction is? What happens when you slide something on a rough surface?”
-
Guide students toward understanding that friction is a force that resists motion, and the rougher the surface, the more friction there is.
-
Then explain how friction fits into Newton’s First Law:
“Newton’s first law tells us that an object will stay at rest or in motion unless acted on by an outside force. Friction is one of those forces—it slows down objects in motion.”
- You may also explain Newton’s Second Law:
“Newton’s second law tells us that the force on an object equals its mass times its acceleration (F = ma). Today, we’ll see how friction is a force that opposes motion and affects acceleration.”
What is Speed and Acceleration?
- You may explain:
“Speed is how fast something moves, and acceleration is how quickly that speed changes. When an object moves faster and faster down a ramp, it’s accelerating.”
Step 1: Setting Up the Ramps
- You may explain:
“We’re going to build ramps today, and we’ll be testing how the surface of the ramp affects the speed and acceleration of a cart while keeping the angle of the ramp the same for every test.”
-
Building the Ramps:
- Students will work in small groups to set up ramps with one fixed angle.
- Each group will be assigned different surface materials (e.g., sandpaper for rough, plastic for smooth, rubber for sticky) to test how friction affects motion.
- Students will place photogate sensors at two points along the ramp to measure the speed of the cart as it moves down the ramp.
-
Placing the Photogate Sensors:
- Guide students to place one photogate at the top of the ramp and another near the bottom.
- Measure the distance between the two photogates, as this will help calculate the speed.
Step 2: Running the Experiment
- You may ask:
“Before we begin, what do you think will happen to the speed of the cart as it moves on different surfaces? Will it move faster on smooth surfaces or rough ones?”
-
Let students make predictions and write them down in their worksheets.
-
Controlled Variables:
- Remind students to keep the ramp angle, cart weight, and distance between photogates the same for a fair test. The independent variable is the surface type.
Recording Data:
- Measuring Speed:
- Roll the cart down the ramp, and the photogate sensors will record how long it takes for the cart to pass between the two points.
- Use the formula for speed:
Speed = Change in distance/Change in time
Worksheet Table:
| Angle of Inclination | Time Between Photogates (s) | Distance (m) | Speed (m/s) |
|---|---|---|---|
| 10° | |||
| 20° | |||
| 30° |
- Students will record the time it took for the cart to travel between the sensors and use the formula to calculate speed.
- Measuring Acceleration:
- Acceleration is the rate at which speed changes. If the cart speeds up as it moves down the ramp, it’s accelerating. The formula for acceleration is:
Acceleration = Change in speed/Change in time
- Guide students through the process of calculating acceleration using their speed data considering that the initial speed of the cart is zero since it was at rest and the final speed is the one we calculated.
Data Table Example:
| Surface Type | Distance Between Sensors (cm) | Time (s) | Speed (cm/s) | Acceleration (cm/s²) |
|---|---|---|---|---|
| Smooth Plastic | ||||
| Sandpaper (Rough) | ||||
| Rubber (Sticky) |
Guided Activity and Follow-Up Questions: (15-20 minutes)
-
Analyzing the Data:
You may ask:
“How did the speed and acceleration change depending on the surface of the ramp? Which surface made the cart move fastest, and why?”
- Students should discuss how friction affects the speed and acceleration, with rough surfaces slowing the cart down.
-
Drawing Graphs:
You may explain:
“Let’s create a bar graph to show how speed changed based on the surface type.”
- Students will create graphs to show the relationship between surface type and speed.
Follow-Up Questions:
- “What does your graph show about the relationship between surface type and speed? Why do some surfaces create more friction than others?”
- “How does this relate to Newton’s laws? Why does friction slow the cart down?”
- “Why is it important to keep the ramp angle constant for this experiment?”
- “What is the independent variable in your experiment? What is the dependent variable?”
Summary and Wrap-Up: (5-10 minutes)
You may summarize:
“Today, we learned how surface type affects the speed and acceleration of a cart. We saw that rough surfaces create more friction, which slows down the cart, while smooth surfaces allow the cart to move faster.”
Real-World Connection:
“These same principles apply in real life when cars drive on rough or smooth roads, or when you ride a bike on different types of surfaces. Friction helps us stop or slow down when needed, but it can also slow us down when we’re trying to move faster.”
Glossary:
- Friction: The force that resists motion between two surfaces.
- Speed: How fast something moves, calculated by dividing distance by time.
- Acceleration: The rate at which an object’s speed changes.
- Photogate Sensor: A device that measures the time it takes for an object to pass through a light beam.
- Newton’s First Law: An object in motion will stay in motion unless acted on by an external force (like friction).
- Newton’s Second Law: The force on an object equals its mass times its acceleration (F = ma).
- Independent Variable: The variable that you change in an experiment (e.g., surface type).
- Dependent Variable: The variable that you measure in an experiment (e.g., speed or acceleration).
- Controlled Variables: The variables that stay constant in an experiment (e.g., ramp angle, cart weight).