Work Done — Homi Bhabha Class 9 Physics MCQs with Solutions
Free Homi Bhabha Class 9 Physics Work Done MCQs with step-by-step solutions (12 questions). Part of Work, Energy & Power. Practise online on Prepizo — no login needed.
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Questions with solutions
Q1 — Work Done · medium · numerical
A force of 20 N moves a body 5 m in the direction of the force. The work done is:
A. 25 J
B. 4 J
C. 15 J
D. 100 J ✓ Correct
Solution: Work $= F \times s = 20 \times 5 = 100$ J.
Q2 — Work Done · hard · theory
A coolie carrying a load on his head walks a distance on a level platform. The work done by him against gravity is:
A. maximum
B. zero ✓ Correct
C. equal to the distance walked
D. equal to the weight of the load
Solution: The load moves horizontally while gravity acts vertically, so the displacement in the direction of the gravitational force is zero — work done against gravity is zero.
Q3 — Work Done · hard · numerical
A force of 10 N acts on a body but the body does not move. The work done is:
A. 0 J ✓ Correct
B. 1 J
C. 10 J
D. 100 J
Solution: Work $= F \times s$; with zero displacement the work done is zero, however large the force.
Q4 — Work Done · medium · theory
Work is done on a body only when:
A. a force acts and the body moves in the direction of (a component of) the force ✓ Correct
B. the body is at rest
C. the body has energy
D. a force acts on the body
Solution: Work requires both a force and a displacement along the force; either alone gives zero work.
Q5 — Work Done · hard · numerical
A body is lifted vertically through 4 m by applying a force equal to its weight of 25 N. The work done against gravity is:
A. 29 J
B. 21 J
C. 100 J ✓ Correct
D. 6.25 J
Solution: Work $= F \times h = 25 \times 4 = 100$ J.
Q6 — Work Done · medium · theory
The SI unit of work is the joule, which is equivalent to:
A. newton per metre
B. newton·metre (N·m) ✓ Correct
C. kilogram·metre
D. watt·metre
Solution: 1 joule = 1 newton × 1 metre (N·m).
Q7 — Work Done · hard · theory
When friction acts on a body opposite to its motion, the work done by friction is:
A. zero
B. infinite
C. positive
D. negative ✓ Correct
Solution: Friction acts opposite to the displacement, so the work it does on the body is negative.
Q8 — Work Done · easy · theory
When a force acts on a body but the body moves in a direction perpendicular to the force, the work done by that force is...
A. Negative
B. Zero ✓ Correct
C. Equal to the force
D. Maximum
Solution: Work = force × distance × cos(angle). When the angle is 90 degrees, cos 90 = 0, so the work done is zero.
Q9 — Work Done · easy · numerical
A force of 10 N moves a box 5 m in the direction of the force. How much work is done?
A. 2 J
B. 50 J ✓ Correct
C. 15 J
D. 500 J
Solution: Work = force × distance = 10 N × 5 m = 50 J, since the force and displacement are in the same direction.
Q10 — Work Done · medium · theory
A man holds a suitcase and walks steadily along a flat, level road. The work done by him against gravity is...
A. Very large and positive
B. Zero ✓ Correct
C. Negative
D. Equal to the weight times the distance walked
Solution: Gravity acts vertically downward while the displacement is horizontal. The angle between them is 90 degrees, so the work done against gravity is zero.
Q11 — Work Done · medium · numerical
A force of 20 N is applied at an angle of 60 degrees to a horizontal displacement of 10 m. The work done by the force is (cos 60 = 0.5)...
A. 173 J
B. 100 J ✓ Correct
C. 200 J
D. 50 J
Solution: Work = F × d × cos(angle) = 20 × 10 × 0.5 = 100 J. Only the component of force along the displacement does work.
Q12 — Work Done · hard · numerical
A 2 kg block is first lifted vertically upward by 3 m and then carried horizontally by 4 m. Taking g = 10 m/s squared, the total work done against gravity is...
A. 80 J
B. 100 J
C. 140 J
D. 60 J ✓ Correct
Solution: Work against gravity is done only during the vertical lift: mgh = 2 × 10 × 3 = 60 J. Carrying the block horizontally is perpendicular to gravity and adds no work against it, so the total is 60 J.