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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 motor does 200 J of work in 10 s. What is the motor’s average power?
    Power = Work / time = 200 J / 10 s = 20 W. Answer: 20 W.
  • 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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