Inertia is the tendency of an object to resist changes in its state of motion. The more mass an object has the greater its inertia.
An object will remain at rest or in a uniform motion unless acted upon by an unbalanced force. What does this mean? If an object is not moving it will remain still. If an object is moving it will continue to move at a constant speed. The situations above will not change unless a force acts on the object.
If all the forces on an object are equal, the force is balanced and there is no motion. (The net force is zero.) If all the forces on an object are unequal, the force is unbalanced and there is motion. (There will be a net force.) The first law states that there can be no movement without a net force.
Imagine a bowling ball and a basketball, both the same size. You want to accelerate them at the same speed. What must you do for this to occur? The basketball has a mass of 10 kg and the bowling ball has a mass of 50 kg A larger force must be applied to the bowling ball for it to accelerate because the bowling ball has a greater inertia. The greater the inertia the greater the ability to resist motion.
Pick one example to write in your notebook from the next three slides.
Lets take a look at a real world example…….. A bowling ball will continue at a constant speed until it hits the pins. At that point, its motion is slowed down or stopped. On the other hand, the pins will remain at rest until hit by the ball. When this happens, the motion of the bowling pins are changed.
Lets look at another example…….. When watching footage of astronauts in space, notice the tools floating, and remain in one spot (as long as there is no force acting on them). If the tools are thrown while doing a spacewalk, they would move in a straight line at a constant speed (until an unbalanced force acts on it).
Vehicle Restraints When a car makes an abrupt stop passengers tend to lunge forward and would probably fly through the window, but the seatbelt prevents this by exerting a force, which stops us from moving any further.