Physics · The potential energy of a spring, conservation of mechanical energy, conservative and non-conservative forces

A spring is kept compressed by a toy car of mass On releasing the car it moves w

A spring is kept compressed by a toy car of mass \( 150 g . \) On releasing the car it moves with a speed of \( 0.2 m s^{-1} . \) So, the elastic potential energy of the spring is

  • A. 3 m J \)
  • B. \( 3 J \)
  • C. \( 1.5 m J \)
  • D. \( 4 m J \)

Step-by-step solution

The elastic potential energy stored in the spring is converted entirely into the kinetic energy of the car (assuming no energy losses). Kinetic energy is given by KE = (1/2)mv^2. With mass m = 150 g = 0.15 kg and speed v = 0.2 m/s, KE = 0.5 * 0.15 * (0.2)^2 = 0.5 * 0.15 * 0.04 = 0.003 J = 3 mJ.
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