Chapter focus
Describe forces as pushes or pulls and explain how they can change motion or shape. Distinguish contact from non-contact forces.
These are original study notes and practice questions prepared for revision. Use your assigned NCERT edition for the complete lesson, diagrams, activities, and exercise wording.
What you will learn
- Explain the main idea: Describe forces as pushes or pulls and explain how they can change motion or shape. Distinguish contact from non-contact forces.
- Use the key terms and relationships in the notes below.
- Show your reasoning and check whether an answer fits the question.
Key ideas and notes
- A force can change an object’s speed, direction, or shape.
- Friction, tension, and a push by touch are contact forces; gravity and magnetic attraction act at a distance.
- Balanced forces have zero resultant; unbalanced forces can change motion.
Worked example
A book resting on a table has gravity downward and support force upward; when balanced, it stays at rest.
Quick revision
A force can change an object’s speed, direction, or shape.
Friction, tension, and a push by touch are contact forces; gravity and magnetic attraction act at a distance.
Balanced forces have zero resultant; unbalanced forces can change motion.
Original practice questions
Try each question first. Open the answer to check your reasoning.
Name the force opposing motion between a sliding box and floor.
Answer: Friction.
Can a force change shape without moving an object?
Answer: Yes; squeezing clay changes its shape.
What is the resultant of equal opposite forces?
Answer: Zero; the forces are balanced.
Chapter summary
Describe forces as pushes or pulls and explain how they can change motion or shape. Distinguish contact from non-contact forces. The key ideas above give you a short revision path; practise explaining them in your own words and revisit any step you could not justify.