Introduction
Newton was the scientist that helped us learn about the motion of objects and the forces acting on them. His three statements often referred to as Newton's first, Second and third laws of motion gave insight into understanding why objects in motion posses certain characteristics. So we will be looking at the first one right now.
Newton's first law of motion.
Newton’s first law states that if a body is at rest or moving at a constant speed in a straight line, it will remain at rest or keep moving in a straight line at constant speed unless it is acted upon by a force source
Explanation
This law helps us understand why objects continue to move if they are in motion already or continues to rest if they are not moving. For objects that are in motion, they will continue to move until an external forces causes them to stop moving. The force that causes a change in the state of this object might be a pull or push force. Whichever one it is, the object in motion would not stop unless such external forces acted on them.
Newton's first law still applies to objects that are at a state of rest. An external force is always needed to cause an object at rest to start moving. Otherwise, such object will remain at a state of perpetual rest. Unless a push or pull force is applied, objects at rest or in motion will continue in their state perpetually.
In real life, There are many examples of using forces to change the state of an object. For example, the forces that could make an object change its state could be the breaks applied to stop a moving vehicle. Or stepping on the accelerator to cause a stopped vehicle to move. Pushing a door could cause it to move forward and open. While pulling back the handles could cause the door to stop moving. There are many other examples of applying forces to cause an object to change its state.
The ability of an object to remain in a state of motion or rest until an external force is applied on it is also known as Inertia.
Why do Objects in motion eventually slow to a stop?
Newton's first law of motion seems not to work in real life. Otherwise, why do objects in motion gradually slow to a halt even when no external forces are applied? Well the law does apply and work in real life. One needs to understand that there are external forces that also act on bodies or objects. Consider two of such forces:
- Frictional forces: Friction is a type of force that exists between two surfaces or objects in contact. This force opposes the relative motion of these objects. There are frictional forces between the tires of a vehicle and the road surface. There are frictional forces between the foot of a pedestrian and the road. This force tend to oppose of stop the motion of the two objects.
Frictional forces does account for the slowing of a vehicle in motion even when the driver has not applied the breaks. For force of friction between the road and the vehicle tire will continue to resist the forward movement of the vehicle such that the vehicle will eventually stop even when the breaks were not applied.
- Force of gravity: The force of gravity pulls objects to the center of the earth. For a vehicle moving on a horizontal road, the force of gravity might have very little or no effect as it mainly acts on the weight of the vehicle. But for a vehicle moving up a hill, the force of gravity would have a big effect as it will be pulling the vehicle back and slowing its motion.
So in the case of an object moving up an inclined plane, the force of gravity could make it to gradually slow down, stop and start rolling backwards.
Inertia in vehicle passengers
We object the application of inertia in many different ways. Passengers inside a vehicle could be a very easy and practical example.
When a stopped car suddenly accelerates, passengers inside the car fall backwards. Why does this happen? Because of inertia. The passengers are at rest and such a body must remain at rest until an external force is applied. So when the driver steps on the accelerator, the vehicle suddenly moves forward. But the passengers fall backwards because they tend to remain at rest if not for the sudden forward movement of the car.
The same thing happens when a speeding car suddenly stops. The passengers fall forwards because an object in motion tends to continue moving. The passengers would fell forward because they tend to continue moving because of inertia, if not for the sudden application of the car breaks.
Conclusion
Newtons first law of motion helps us to understand the change in state of objects, the forces that act on them and some of the characteristics they possess.
