National League for Nursing (NLN) Science Practice Exam

If an electromagnet holds a 1,500-kg car at a height of 25 m, which statement is false after a power outage?

1. The car had a potential energy of 367.5 kJ.

2. 367.5 kJ of potential energy is converted to kinetic energy.

3. The car still has a potential energy of 367.5 kJ when it hits the ground.

4. The potential energy is converted to kinetic energy and then to sound energy.

The correct answer is: The car still has a potential energy of 367.5 kJ when it hits the ground.

The statement that the car still has a potential energy of 367.5 kJ when it hits the ground is indeed false because potential energy is defined as the energy stored in an object due to its height above the ground. Once the car descends to the ground, its height effectively becomes zero, which means its potential energy also becomes zero. Before the power outage, when the car is suspended at a height of 25 m, its potential energy can be calculated using the formula \( PE = mgh \), where \( m \) is the mass in kilograms (1,500 kg), \( g \) is the acceleration due to gravity (approximately 9.81 m/s²), and \( h \) is the height in meters (25 m). Performing the calculation yields a potential energy of approximately 367.5 kJ. After a power outage, if the electromagnet fails, the car will begin to fall. As it falls, the potential energy is converted into kinetic energy, which can be described by the conversion of energy principles. When the car hits the ground, all of the potential energy is transformed into kinetic energy, assuming negligible air resistance until it reaches the ground. Additionally, when the car strikes the ground, some