Physics - Newton's Three Laws of Motion

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Newton’s First Law of Motion (also known as the Law of Inertia) is that in order for motion to occur with any object or to make that object move, there must be a force applied to that object. This force that is applied is known as inertia. In addition, in order for movement to stop its motion, there must be a sufficient amount of force applied to stop the object’s forward momentum. Force is any action that will cause an object to change its speed (velocity) and/or the direction in which it is moving. Momentum is “mass in motion.”

An example of Newton’s First Law: Objects will remain in a state of rest (no movement) unless and until a force is applied to it such as an airplane. Without the force provided by jet fuel, the airplane would not move. The amount of force that is used by the jet engines propels the airplane forward and the continued force (inertia) increases the velocity of the airplane until it is able to lift off of the ground. If you remove that force, the plane will fall and cease its motion. Remove the force, you stop the motion.

Newton’s Second Law of Motion is that there must be a defined relationship between force, acceleration and mass. Acceleration is the rate of change through time while mass is the quantity of inertia that is exhibited or possessed by an object. The stronger the force exerted upon an object will directly affect the acceleration of an object. In addition, the weight of an object, or the mass of an object will also affect the degree to which that object will accelerate. Finally, other forces come into play that can impact the acceleration of an object.

An example of Newton’s Second Law: Looking again at the airplane discussed in Newton’s First Law, the mass of the airplane directly relates to the amount of force that must be exhibited in order to move the plane forward and then to accelerate its velocity. This acceleration of the mass also encounters the mass of wind which must be overcome in order for the plane to reach the required velocity (speed) in order to be lifted off of the ground. It must also overcome the force of gravity which wants to keep the airplane on the ground. In order for the airplane to move as it is intended, it must have a defined relationship between the amount of force needed, the acceleration needed and how much mass must be pushed through and carried in order for the plane to take flight.

Newton’s Third Law of Motion is the simple understanding that for every action, there is an equal and opposite reaction. In other words, if you pull on a rope, the rope is also going to be pulling back on you by way of its mass or, in other words, the gravity of the rope will pull back on you. Gravity is the force of attraction that exists between two objects. It is gravity that will cause rocks to fall from a cliff.

With this quick review of Newton’s Three Laws of Motion, see if you can find the right answers to the following ten questions. Some can be tricky so pay attention to what action or actions are taking place in order to determine the correct law it falls under.