Year 7 Science · Unit 3 · Lesson 1
Challenge Worksheet
Learning Goals
What if…?
Scenario
Imagine that scientists discover gravity has changed its fundamental nature overnight: it is now a contact force. This means gravity can only act when two objects are physically touching — just like friction or the normal force. Earth's mass, the planets' masses, and all their speeds remain exactly the same. Only gravity's "reach" has changed: it now requires direct contact to operate.
Using what you know from this lesson about contact vs non-contact forces and how gravity keeps planets in orbit, predict and explain what would change about the Solar System and everyday life on Earth. Use scientific terms (contact force, non-contact force, orbit, gravity, vector) in your answer. Consider at least two different consequences.
1. At the atomic level, the lesson says that contact forces like friction and the normal force are actually examples of which fundamental force? Explain why this blurs the distinction between "contact" and "non-contact" forces.
2. A force arrow diagram shows two arrows on a ball: one pointing right (length 3 cm) and one pointing left (length 3 cm). A second diagram shows the same ball but the right arrow is 5 cm and the left arrow is 3 cm. Describe what is different about the ball's motion in each case, and explain the role of the vector nature of force in your answer.
Wrap Up
In one sentence, what was the main idea of this lesson?