This concept can be seen in many different examples in nature. One of which is a person running at full speed. This person has a mass, and a velocity that remains constant. Wanting to change their velocity will require an external force to act on the person. This would be the friction the ground exerts on the runner as he or she slows down. The difficulty of slowing down is related to the weight of the person running. The heavier the person, the more difficult it will be for them to stop. The lighter the person, the easier it will be to stop. We all experience this every day. The reason for this, is because of the inertia of the moving object. An object will continue to move at a constant velocity unless acted upon on an external force. The magnitude of this force is dependent on the weight of the object. It makes logical sense to think more mass will require more energy. The inertia of an object is it’s resistance to change in motion, if an object is stationary, it will stay stationary. If an object is moving, it will continue moving. Unless of course acted upon by an external force.
One interesting example of this is a truck with heavy cargo in the back. If the truck is travelling at 100km an hour, so is the cargo. If the cargo is not tightly secured to the truck, it can result in a dangerous accident. As the truck rapidly decelerates to a stop, its velocity is changing. If the cargo is not secured to the truck, there will be little external force acting on the cargo (which is still traveling at 100km/h, while the truck is at a slower speed), causing the cargo to continue at its 100km/h velocity as the truck rapidly decelerates. This can cause the cargo to