Imagine you are going on a family trip, and your parents ask you to load the luggage onto the car’s roof rack. The luggage sits on the porch, and has inertia: it will not move until you apply enough force to move it. You decide to overcome the inertia of the luggage and load the car.

Question

Imagine you are going on a family trip, and your parents ask you to load the luggage onto the car’s roof rack. The luggage sits on the porch, and has inertia: it will not move until you apply enough force to move it. You decide to overcome the inertia of the luggage and load the car.

Now you are off on your trip. As the car speeds down the road toward your destination, your dad asks you why there are luggage straps still in the back seat. Just as you realize why, a dog runs across the road and your dad slams on the brakes. The dog manages to escape, but the luggage flies forward off the roof rack, landing far ahead of the car on the road. You again recall the law of inertia: an object in motion (like luggage on a speeding car) will stay in motion unless acted upon by a sufficient force (provided by luggage straps). As your dad fumes, you explain Newton’s first law to him to divert his attention.

Answer 1

Newton's first law of motion, also known as the law of inertia, states that an object at rest will stay at rest, and an object in motion will stay in motion with the same speed and direction unless acted upon by an external force. In this case, the luggage on the roof rack was initially at rest, but when the car started moving, it gained inertia and remained in motion. However, when your dad slammed on the brakes, the car experienced a force that caused it to decelerate rapidly. According to Newton's first law, the luggage on the roof rack continued to move forward with the same speed and direction it had before the brakes were applied. Since there were no sufficient forces, such as the luggage straps, to counteract this motion and keep the luggage in place on the roof rack, it flew forward and landed on the road. This is a clear example of how an object's inertia, as described by Newton's first law, can lead to unexpected consequences when not properly accounted for.