3. Complete Activity 10.3 (Page 114).
• Think of situations when the object is not displaced in spite of a force acting on it.
• Also think of situations when an object gets displaced in the absence of a force acting on it.
• List all the situations that you can think of for each.
• Discuss with your friends whether work is done in these situations.
Answer:
Object is not displaced in spite of a force acting on it:
(i) Holding a heavy object stationary above the ground: In this casethe force of gravity acts downwards on the heavy object, but there is no displacement. Hence work done is zero.
(ii) Pushing against a wall: In this case there is a force on the wall, but no displacement of the wall. Hence, work done is zero.
Object gets displaced in the absence of a force acting on it:
(i) Object moving with constant velocity: In this case the net force on the body is zero, but there is displacement of the object, Hence, work done is zero.
Note: Leaves falling from trees, a ball rolling down an inclined plane, book dropping to the ground when you release it – in all these situations it may seem that there is no external force acting on it, the force of gravity does act on them.
“• Think of situations when the object is not displaced in spite of a force acting on it.
• Also think of situations when an object gets displaced in the absence of a force acting on it.
• List all the situations that you can think of for each.
• Discuss with your friends whether work is done in these situations.” – Solved.
Related Links:
Solution to Activity 10.1
Solution to Activity 10.2
Solution to Activity 10.3
Solution to Activity 10.4
Solution to Activity 10.5
Solution to Activity 10.6
Solution to Activity 10.7
Solution to Activity 10.8
Solution to Activity 10.9
Solution to Activity 10.10
Solution to Activity 10.11
Solution to Activity 10.12
Solution to Activity 10.13
Solution to Activity 10.14
Solution to Activity 10.15
Solution to Activity 10.16
Solution to Activity 10.17
Solutions to Chapter 10 Work and Energy
