Question

An electromagnet is holding a 1,500-kg car at a height of 25 m above the ground. The magnet then experiences a power outage, and the car falls to the ground (without injuring anyone). Which of the following is false? (A) The car had a potential energy of 367.5 kJ. (B) 367.5 kJ of potential energy is converted to kinetic energy. (C) The car still has a potential energy of 367.5 kJ when it hits the ground. (D) The potential energy is converted to kinetic energy and then converted to sound energy.

Answer 1

The false statement in the provided options about the falling car scenario is (C). When the car lands, it no longer possesses the potential energy due to height -- it's been converted into kinetic energy, and subsequently into sound, heat and material deformation.

Step-by-step explanation:

The question pertains to the concept of potential and kinetic energy and how they interact during a fall, in context of physics. When the car is held above the ground, it has potential energy due to its height. The energy is calculated with the formula PE = mgh, where m is the mass, g is acceleration due to gravity (approx 9.8 m/s²), and h is height. For a 1500 kg car at 25 meters, this yields approximately 367.5 kJ of potential energy.

When the car begins to fall, this potential energy starts converting into kinetic energy, as the vehicle begins to move faster. By the time the car reaches the ground, if we ignore effects of air resistance, almost all the potential energy has been converted into kinetic energy - hence the statement (B) is correct

However, the option (C) is false. Once the car hits the ground, it no longer possesses any potential energy from height, assuming the defined 'ground' as our point of reference for potential energy. The energy would have been transformed into kinetic, and then as the car comes to a stop, into sound, heat and deformation of the materials (which accounts for the 'crash'), thus point (D) is correct.

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