How is inertia related to force

Inertia and Mass 1


Mass has an effect on almost all aspects of our lives. Inertia, the resistance to change in motion, is one property of all matter that is affected by changes in mass. This can be observed in the varying resistance to motion of objects with different masses.


1 kg weight

0.5 kg weight


Spring scale (5 N) or 2 rubber bands


Tie a piece of string in a bow around each of the weights.

Attach the spring scale to the 0.5 kg weight by hooking it through one of the loops of the string.

Pull the weight across the table by pulling on the spring scale. Notice how much force is used.

Use the spring scale to pull the 1 kg weight across the table. Notice how much force is used.

If using rubber bands instead of spring scales and string, wrap one rubber band around one weight. Cut the other rubber band to make a straight piece. Tie the straight piece of rubber band to the one wrapped around the weight. Pull the straight rubber band to move the weight and measure how far the band had to be stretched. Repeat this with the other weight using the same rubber bands. Compare the length the band had to be stretched to move each weight.


For which weight was more force required to move it? For which weight did the rubber band have to be stretched further to just begin to make it move?

Which weight had the most inertia?

What was different about the weight with more inertia and the weight with less inertia?

How can we relate the properties of mass and inertia?


Both the weights have inertia and both have mass. However, the larger weight has more inertia because mass and inertia are related. The more mass an object has the more inertia it has. The force applied from spring scale, or the rubber band, acted as the outside force to cause motion in the weights and it was easy to see that more force was needed to overcome the inertia of the heavier weight.