A disc of radius 2 m and mass 100 kg rolls on a horizontal floor. Its centre of mass has speed of 20 cm/s . How much work is needed to stop it? - Physics MCQ NEET 2019 2026 | ExamTest.live

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A disc of radius 2 m and mass 100 kg rolls on a horizontal floor. Its centre of mass has speed of 20 cm/s . How much work is needed to stop it?

Solution & Step-by-step Explanation

The work needed to stop the disc is equal to its total kinetic energy (K_{t o t a l}).For a rolling body: K_{t o t a l} = \frac{1}{2} M v^{2} (1 + \frac{k ^{2}}{R ^{2}}) For a disc, \frac{k ^{2}}{R ^{2}} = \frac{1}{2} .Speed v = 20 cm/s = 0.2 m/s . K_{t o t a l} = \frac{1}{2} \times 100 \times (0.2)^{2} \times (1 + \frac{1}{2}) K_{t o t a l} = 50 \times 0.04 \times 1.5 = 2 \times 1.5 = 3 J

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A disc of radius 2 m and mass 100 kg rolls on a horizontal floor. Its centre of mass has speed of 20 cm/s . How much work is needed to stop it?

3 J

30 kJ

2 J

1 J

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