Inertia Case Studies in Motion

Teach each law with its sheet, then use Force Pairs Versus Balanced Forces to clear up the most common confusion. Use the crash sheet as a capstone that uses all three laws.

Apply inertia to a deep space probe and a bus by drawing net force arrows for each case. Inertia is the tendency of an object to keep doing what it is doing, at rest or moving steadily, unless a net force acts on it. The directions on the page read: Read the three cases. Then complete the diagrams and answer the questions on page 2. An answer key is included.

Yes, both. We made it for 7th grade forces and motion, and it works the same at home or at school. At home, a student can work through it alone and then go over it with you, which shows quickly what is solid and what needs another look. In class it works as independent practice, homework or a warm-up, and you can print one copy or a full set.

An object keeps moving at the same speed in a straight line, or stays at rest, unless a net force acts on it. In a crash, an unbelted rider keeps moving until something applies a force.

The acceleration of an object depends on the net force and the mass, a = F / m. A bigger force gives more acceleration, and a bigger mass gives less.

When two objects interact, they push on each other with forces equal in size and opposite in direction. These forces act on different objects, so they never cancel.