CER Writing: Forces & Motion
Example CER
Question: How does friction affect the motion of objects?
Claim: Friction slows down and eventually stops moving objects.
Evidence: In our experiment, a toy car rolled 50 cm on a smooth floor but only 12 cm on a rough towel. The car stopped completely on all surfaces instead of rolling forever. Rough surfaces like carpet and sandpaper stopped the car faster than smooth surfaces.
Reasoning: This shows that friction acts against motion because the rough surfaces created more friction, which removed energy from the car faster. Without friction, the car would keep rolling. The data proves that more friction means shorter distances, so friction is a force that opposes motion.
Practice Questions
1. Which is the best CLAIM for "Why do objects fall to the ground?"
A) Objects fall
B) Objects fall because gravity pulls them toward Earth
C) I see things fall
D) The ground is there
Answer
B) - This claim directly answers "why" with a specific scientific explanation.
2. Which is the best EVIDENCE for "Smooth surfaces have less friction"?
A) Smooth surfaces look nice
B) The car rolled 50 cm on tile but only 22 cm on carpet
C) I think friction is interesting
D) Surfaces can be smooth or rough
Answer
B) - This provides specific data comparing two surfaces.
3. A student writes: "The car went farther on the smooth surface." This is:
A) A claim
B) Evidence
C) Reasoning
D) A hypothesis
Answer
B) Evidence - This is an observation or data from an experiment.
4. Which shows good REASONING?
A) The car stopped
B) I did the experiment
C) This shows friction slows motion because rough surfaces create more friction
D) Forces are pushes or pulls
Answer
C) - This explains HOW the evidence connects to the claim.
5. What makes data strong evidence?
A) Using lots of adjectives
B) Specific numbers and measurements
C) Using your opinion
D) Making it up
Answer
B) - Specific numbers (like "50 cm") make evidence stronger than vague statements.
6. "In our ramp experiment, we found..." is a good way to start:
A) A claim
B) Evidence
C) Reasoning
D) A question
Answer
B) Evidence - This introduces data from an experiment.
7. "This demonstrates that..." helps introduce:
A) A claim
B) Evidence
C) Reasoning
D) A title
Answer
C) Reasoning - This phrase connects evidence to your claim.
8. How many pieces of evidence should a good CER include?
A) 0
B) 1
C) 2-3
D) 100
Answer
C) 2-3 - Multiple pieces of evidence make your argument stronger.
9. What should come LAST in a CER?
A) Claim
B) Evidence
C) Reasoning
D) The question
Answer
C) Reasoning - Reasoning explains the connection and usually comes at the end.
10. Why do scientists use CER?
A) To make writing longer
B) To clearly explain findings with evidence and logic
C) Because it's required
D) To confuse people
Answer
B) - CER helps scientists communicate their thinking clearly and logically.
Your Turn!
Write a CER for this question:
"How does the weight of an object affect how much force is needed to move it?"
- Claim: Heavier objects need more force because...
- Evidence: (Think about pushing empty vs. full boxes)
- Reasoning: This shows that...
Next Steps
- Use your ramp experiment data to write a CER
- Have a partner check your CER for all three parts
- Continue to the Unit Checkpoint