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300 J of work is done in sliding a 2 kg block up an inclined plane of height 10 m. Work done against friction is (take g=10 m s⁻²)

Asked in NEET 2006 · Work done by friction

Answer: (3) 100 J

Step-by-step solution

Given: W=300 J supplied, m=2 kg, h=10 m, g=10 m s⁻², and the block is slid up (no kinetic energy left over).

Idea: the work supplied goes partly into lifting the block and the rest into friction.

Potential energy gained =mgh=2×10×10=200 J.

W_supplied=Δ U+W_friction.

W_friction=300-200=100 J.

Notice the length of the incline never enters; only the height matters for the lift.

Why the other options are wrong

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