Question

work is done or not?

1. a rocket accelerates through space yes no
2. pedaling a bicycle forward yes no
3. holding a heavy object stationary yes no
4. pushing a wall that doesnt move yes no
5. a book falls off a table and free falls to the ground yes no
6. carrying a box while walking on a level surface yes no
7. a teacher applies a force to a wall and becomes exhausted yes no
8. doctor moving patient in a wheel chair yes no
9. a stack of books is carried at waist level across a room yes no
10. an object moving on a frictionless surface without any force acting on it yes no

Explanation:

Step1: Recall the work formula

Work \(W = F\times d\times\cos\theta\), where \(F\) is force, \(d\) is displacement, and \(\theta\) is the angle between force and displacement. If \(d = 0\) or \(\cos\theta=0\) (force perpendicular to displacement), \(W = 0\).

Step2: Analyze each case

• 1. A rocket accelerates through space: Force (thrust) causes displacement. \(W

eq0\).

• 2. Pedaling a bicycle forward: Force (from pedaling) causes displacement. \(W

eq0\).

• 3. Holding a heavy object stationary: \(d = 0\). \(W = 0\).
• 4. Pushing a wall that doesn’t move: \(d = 0\). \(W = 0\).
• 5. A book falls off a table and free - falls to the ground: Force (gravity) causes displacement. \(W

eq0\).

• 6. Carrying a box while walking on a level surface: Force (vertical, to hold the box) and displacement (horizontal) are perpendicular (\(\cos90^{\circ}=0\)). \(W = 0\).
• 7. A teacher applies a force to a wall and becomes exhausted: \(d = 0\). \(W = 0\).
• 8. Doctor moving patient in a wheel chair: Force (to move the wheelchair) causes displacement. \(W

eq0\).

• 9. A stack of books is carried at waist level across a room: Force (vertical, to hold the books) and displacement (horizontal) are perpendicular (\(\cos90^{\circ}=0\)). \(W = 0\).
• 10. An object moving on a frictionless surface without any force acting on it: \(F = 0\). \(W = 0\).

Answer:

1. YES
2. YES
3. NO
4. NO
5. YES
6. NO
7. NO
8. YES
9. NO
10. NO