Investigation Lab: Forces in Action
📖 Learn
In this laboratory investigation, you will design and conduct experiments to explore how forces affect the motion of objects. Scientific investigation follows a systematic process that allows us to gather reliable evidence.
The Scientific Method in Force Investigations
When investigating forces, scientists follow these steps:
- Ask a Question: What do you want to find out about forces?
- Research: What do Newton's laws predict should happen?
- Form a Hypothesis: Make a testable prediction
- Design an Experiment: Plan how to test your hypothesis
- Collect Data: Record observations and measurements
- Analyze Results: Look for patterns in your data
- Draw Conclusions: Did your results support your hypothesis?
Variables in Force Experiments
Every experiment involves three types of variables:
- Independent Variable: What you change on purpose (e.g., the amount of force applied)
- Dependent Variable: What you measure as a result (e.g., acceleration, distance traveled)
- Controlled Variables: What you keep the same (e.g., mass of object, surface type)
Lab Safety Guidelines
- Clear your workspace of unnecessary items
- Wear safety goggles when using projectiles or rolling objects
- Keep pathways clear to prevent tripping
- Handle equipment carefully to avoid damage
- Report any accidents to your teacher immediately
💡 Examples
Example Investigation 1: Testing Newton's Second Law
Question: How does mass affect the acceleration of an object when the same force is applied?
Hypothesis: If more mass is added to a cart, then it will accelerate less when the same force is applied.
Materials: Dynamics cart, track, spring launcher, masses, stopwatch, meter stick
Procedure:
- Set up the track on a level surface
- Mark start and end points 1 meter apart
- Launch the empty cart with the spring launcher (always pull back the same amount)
- Record the time to travel 1 meter
- Repeat 3 times and calculate average
- Add 100g mass and repeat steps 3-5
- Continue adding mass in 100g increments
Example Investigation 2: Friction Forces
Question: How does surface texture affect friction force?
Hypothesis: Rougher surfaces will require more force to move an object than smoother surfaces.
Materials: Wooden block, spring scale, various surfaces (sandpaper, carpet, tile, wax paper)
Procedure:
- Attach the spring scale to the wooden block
- Place the block on the first surface
- Pull horizontally until the block just starts to move
- Record the force reading
- Repeat 3 times and calculate average
- Test each surface the same way
✏️ Practice
Complete these practice problems to prepare for your own investigation.
1. A student wants to test how the angle of a ramp affects how far a ball rolls after leaving the ramp. Identify:
- a) The independent variable
- b) The dependent variable
- c) Two variables that should be controlled
2. Write a testable hypothesis for the following question: "Does the shape of an object affect how fast it falls?"
3. A student collected the following data when testing Newton's Second Law:
| Mass (kg) | Trial 1 Time (s) | Trial 2 Time (s) | Trial 3 Time (s) |
|---|---|---|---|
| 0.5 | 1.2 | 1.1 | 1.3 |
| 1.0 | 1.8 | 1.7 | 1.9 |
| 1.5 | 2.3 | 2.4 | 2.2 |
Calculate the average time for each mass.
4. Why is it important to conduct multiple trials in an experiment?
5. A student is testing how different amounts of force affect the distance a toy car travels. What should the student keep constant during this experiment?
6. Identify the error in this experimental design: "I will test how mass affects acceleration by pushing different carts with different masses as hard as I can."
7. A student hypothesized that heavier objects fall faster than lighter objects. After dropping objects of different masses from the same height, she found they all hit the ground at the same time. What should she conclude?
8. Design a simple experiment to test whether the mass of a pendulum bob affects its swing period. Include your hypothesis, variables, and a brief procedure.
9. Look at the data table in question 3. Based on the pattern in the data, predict what the average time might be for a mass of 2.0 kg. Explain your reasoning.
10. A student measured the following friction forces for a 1 kg block on different surfaces: wood (4.2 N), carpet (6.8 N), tile (2.1 N), sandpaper (8.5 N). Rank these surfaces from highest to lowest friction.
✅ Check Your Understanding
Question 1: What is the purpose of a controlled variable in an experiment?
Show Answer
Controlled variables are kept constant so that you can be sure any changes in the dependent variable are caused by changes in the independent variable, not by other factors.
Question 2: Why should a hypothesis be testable?
Show Answer
A testable hypothesis can be supported or disproved through experimentation and data collection. If a hypothesis cannot be tested, there is no way to determine if it is correct.
Question 3: How does repeating trials improve the reliability of experimental results?
Show Answer
Repeating trials helps identify and reduce the impact of random errors. By calculating an average from multiple trials, you get a more accurate representation of the true value.
🚀 Next Steps
- Complete your own forces investigation using the scientific method
- Review how to identify variables in experimental designs
- Move on to the next lesson to learn how to create graphs from your data
- Practice writing clear hypotheses for different force scenarios