ASVAB Science Study Guide Part 3

Physics

Newton’s Laws of Motion

Newton’s first law of motion: An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force. For example, a ball resting on the grass will remain resting on the grass until a force is applied, such as a foot. After the kicked ball begins rolling, it will continue to roll until a force (friction) causes it to slow down. Newton’s first law of motion is also called the law of inertia. Inertia is the tendency of an object to resist change in motion.

Newton’s second law of motion: The acceleration of an object is equal to the net force acting on it divided by the object’s mass. According to this law, acceleration is produced when a force acts on a mass. The greater the mass of the object being accelerated, the greater amount of the force needed to make the object accelerate. This is why it takes more force to move heavier objects the same distance as lighter objects. Using this law, acceleration can be calculated as follows:

Newton’s third law of motion: For every action, there is an equal and opposite reaction. In other words, when one object exerts a force on a second object, the second object exerts an equal and opposite force on the first object. The two forces are called action and reaction forces. The force of your bumper car on the other bumper car when you crash into it is the action force. The force of the other bumper car on your car is the reaction force.

Kinetic Energy vs. Potential Energy

Energy can be classified into two general types: kinetic energy and potential energy.

Kinetic energy: The energy that an object possesses due to its motion.  Some examples of kinetic energy include a thrown baseball, a flying airplane, and a flowing river.

Potential energy: The energy stored by an object as a result of its position. Some examples of potential energy include a compressed spring, a lifted weight, and a stretched rubber band.

 

 

Forms of Energy

 

  • Mechanical energy is the energy associated with the motion and position of objects. It is the sum of an object’s potential and kinetic energy.
  • Thermal energy is the total potential and kinetic energy related to the motion of subatomic particles in an object.
  • Chemical energy is the energy stored in chemical bonds. Cars use the chemical energy stored in gasoline.
  • Electrical energy is the energy associated with electric charges. Batteries convert chemical energy to electrical energy.
  • Electromagnetic energy is energy that travels through space in the form of waves, such as visible light.
  • Nuclear energy is the energy stored in atomic nuclei. This includes nuclear fission and nuclear fusion.

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