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Principle of Inertia
Newton's First Law is also referred to as the Principle of Inertia. Inertia is the tendency of an object to resist any change in its motion.
Objects with greater mass have greater inertia. For example, if you were to roll a bowling ball and a tennis ball, it would take more force to stop the bowling ball than the tennis ball because it has more inertia.
You may have noticed road signs like the one below. It warns cyclists of embedded train tracks ahead. A bike tire could be stopped or slowed quickly by the bumps, which could send the cyclist flying forward. This forward propulsion is due to the fact that your body wants to continue moving in the motion. If a car stopped or slowed quickly, your seat belt would jerk you back. However, in a bike, you don't have a seat belt or similar restraint, so your body would continue moving forward because of inertia.
