WORK POWER ENERGY AND SIMPLE MACHINE

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Rina pushes a box with a constant horizontal force of 10 N over a distance of 2 m. How much work does she do?

Work = F · d = 10 N × 2 m = 20 J. Answer: 20 J.

A student holds a 12 kg backpack stationary for 5 minutes. How much work is done by the student on the backpack?

No displacement ⇒ work = 0 J. Even though force (supporting weight) exists, displacement = 0.

A 2 kg ball moves at 3 m/s. What is its kinetic energy?

KE = ½ m v² = 0.5 × 2 × (3²) = 1 × 9 = 9 J. Answer: 9 J.

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